As per the chat meet-n-greet and the new war information, this is how/where I see Cedric fitting into specifics. Mods, if any of this needs to be tweaked, please just let me know.
Cedric's War Timeline
Aug. 2001 - April 2002 -- Cedric travels around Canada/the U.S., talking to various First Nations tribes, soliciting help. This takes time (Indians don't do anything in a hurry).
June 2002 -- A council of native Elders and Medicine Men meet at White Mountain, Arizona. They elect to join the war against Voldemort and send sorcerer-fighters (Aurors) to assist. There aren't a lot of them but it's a different kind of magic, and a symbolic act of solidarity. There were about 13 all together -- a nice witchy number. (g) Incidently, and following Ojibway tradition, the natives called Voldemort "The White Wendigo" (cannibal spirit), even if he didn't literally eat human flesh.
July 2002 -- Official arrival of Indian 'Aurors' at London Ministry. This is when word would have got back to England that he's alive.
Aug. 2002 -- Via post from his old denmate Peter Adamson, he learns that Cho Chang was killed in the attack on Diagon Alley in September of 2000. Although never officially in the order, when the attack began, she ran towards it instead of away, intending to fight, and was cut down almost immediately. Cedric doesn't know who killed her, but he'd like to find out. Also he hears that their denmate Scott Summers became an Auror and was killed defending Azkaban in August of 2001, and Ed Carpenter, who went on to play professional Quidditch, was killed at the Quidditch exhibition match when Death Eaters attacked back in April of 1999. Peter is very angry at Cedric for not having written in almost five years to tell anybody he was alive -- accuses him of hiding. Cedric feels guilty and is reluctant to explain. Gwen has to step in to tell Peter the whole story; Peter and Cedric eventually make up, but Peter remains a bit cool towards Cedric.
On Cho: Although he hadn't been interested in Cho romantically for some time, he felt very guilty, blaming himself for getting her into the war. Peter told him that Cho fought in his name, and Cedric fears he became an enshrined memory -- the perfect boyfriend that he never actually was. (Not that he was a bad one, but nobody is perfect.) Peter did tell Cedric that Cho had dated first Harry for a while, then Michael Corner, but that none of those relationships worked out and she was known for being a bit unstable by the end.
July 2003 -- Peter is killed in the battle at Liverpool (his home) ... but Cedric doesn't hear about this until four months later when he's back and tries to look Peter up because he stopped hearing from him.
Nov. 2003 -- Cedric returns to England, and goes immediately home to Ottery St. Catchpole. His family's land is a sizable tract of 15-20 acres, well south of the rives, around I street and eastish-south, between the Lovegoods and Susan Bones' farm. The Diggories have lived there since the late 1700s. (It'll be on the new map.) There is nothing left of the house but the foundation. The barn, however, was spared. In it, he found the tent his father took to the World Cup back in '94. The well also survived and is unspoiled. And there's an old outhouse that hadn't been used in some years, but is now repaired. Cedric cleaned up the old house foundation and set up his tent on it.
Just a few days later, while in Diagon Alley shopping for pots, dishes and things he didn't bring with him, the place is attacked. Ironically, he doesn't find himself running to fight, but trying to grab as many people as he can and get them out of there.
Thus begins his rescue and refugee work. While some of those who survived had just been there shopping like him, a number lost everything. He takes these people back to Ottery St. Catchpole. He may not have much, but he does have land -- and a barn where people can sleep out of the winter cold. (See below for Cedric's refugee camp.)
Dec. 2003 -- When things calm down a bit, Cedric makes a trip to Liverpool to find Peter, and learns he's dead. Between the double blow of having just left his fiancée and now losing his last remaining good friend from before, Cedric is deeply depressed and remains so through the rest of the winter. He throws himself into refugee work, and is drinking too much. This levels off by summer. He stops looking half the time like something his cat dragged in.
From Dec. 2003 - Nov. 2004 -- Cedric has run his relief shelter. This is his MAIN contribution to the war effort. He fought in one skirmish (May 2004), but under pressure, his 'mental misfiring' becomes more pronounced. He ended up having to be rescued himself, and was carefully kept away from any combat after. As far as the Order/Ministry/TPTB were concerned, he was much more effective doing relief work. (Very Hufflepuffian of him, I know.)
Now that the need for the shelter has faded/is gone, he's a bit at a loss as to what to do with himself -- figures he should get a paying job somewhere so he can think about rebuilding his house and quit living in a tent.
His immediate [personal] concern as the game begins: Getting electric, gas and phone lines laid. The Diggory house was a very old stone Wizarding country home, never 'modernized.' They had plumbing and that was about it. Back to the foundation, Cedric figures this is a good time to update to the 21st Century.
Cedric's Refugee Camp: The barn stalls offered semi-privacy for about 15 families/individuals. The well offered clean, fresh water, and there were two (very large) taps/sinks in the barn, meant originally for cleaning tack, buckets, etc. One is in the tack room, the other at the other end of the barn. The plumbing still works. They rigged an area outside near the tack room, adjusting the plumbing and fixing it with a permanent obscurification spell, to offer a shower. They eventually hijacked an old-fashioned stove from a mostly-leveled Muggle house and got that set up in the tack room to do some cooking. By this point, the barn has been pretty thoroughly worked over and doesn't look much like a barn inside. The aisles even have some mismatched carpet that was scrounged at some point from destroyed houses, curtains hang in front of the stall doors, etc.
Supplies: Amos and Lucy Diggory's main contribution to the war effort has been in the way of funding Cedric's efforts, and getting clothes and other donations into the country. I'm assuming the Canadian Ministry and American Department of Magic (and probably other countries on the continent) did arrange formal relief efforts. But paperwork can get in the way (boy, can it get in the way). Frustrated and annoyed, Amos (being Amos) arranged to collect (unofficial) donations, stored them in a rental garage, and shipped them to his son in three big deliveries. As is often the case with donated supplies, some was unusable junk, but they received enough blankets, pillows, winter supplies and other clothes, plus assorted pots, pans, kettles and other small household supplies (no large items) for anyone who spent time in Cedric's refugee camp to have collected a few basic necessities before moving on.
I'm assuming there would also have been supplies/funds from more formal channels as well, via the Ministry, etc. I'm not sure if Cedric would have any access to these. His relief effort is pretty informal -- but more rapid/effective because he doesn't have to deal with paperwork.
Only those arriving with virtually nothing but the clothes on their backs and a few salvaged items would have gone to the shelter. It really was designed for disaster relief, not mooching. Cedric worked with Wayne Hopkins to get people into more permanent shelter quickly. The barn was an emergency way-station. I'm assuming no one spent more than a few days to a few weeks there, and weeks only in cases where a lot of people arrived at once and had to be settled.
NOTE TO PLAYERS:
If you think you might have gone through Cedric's shelter, please let me know below, so I have some idea as the game begins who Cedric has interacted with. (I know Wayne, I know Penelope.)
If you think your character would have been helping him out in some capacity, please also let me know. A relief effort like this would take more than one person. He wasn't doing it all himself. Fate and inheritance put him in a position to start it, but he'd have taken whatever help he could get.
Last, if you think your character would still be in the barn (very newly arrived or such), please let me know. Otherwise, I'll assume Cedric is now living out there alone. I'm assuming most people can now bypass an emergency shelter in favor of taking over abandoned property.