I don't know how Mamma Mia works but from what I've seen in the video, Chanyeol is just a guest. No sign of his mum and sister. Though, isn't it a bit too early to introduce his family to the world?
Thanks to nanikore-lj [Trans] Chanyeol on Mamma Mia :
"Chanyeol said that after receiving his salary recently(‘exact settlement fees’ to be more accurate), he bought something that he’s been wanting to buy for some time. It was a desk."