Strapped in a tin can
Flying to a northern land
I gain sympathy
for plastic paratroopers
tangled in neighborhood trees.

( paratroopers? )

If one truly finds
the world in a grain of sand
then universes
resound with every load
my truck adds to my castle.

Tiny steam roller
so very effective at
flattening my roads --
I wonder how well you'd work
at rolling out my pie dough?

With my steam shovel
I excavate basements
for the whole city.
And when barbarians come
it works as a catapult!

This beautiful day
the city streets are empty.
They've gone to the beach
where the horde of tiny trucks
builds fantastic sand castles.

It's opening night,
The dignitaries arrive
In their gleaming cars.
Of course, in my sandbox town
They are all yellow dump trucks.

Puddles like oceans
Devour sandy skyscrapers
As April rains fall.
Come afternoon sun shining
They will rise beneath rainbows!

ETA: Ok, I know no rewrites, I know, but the fourth line is making my teeth ache.
( A slightly different final couplet )

Like metal ducklings,
tiny trucks follow large ones
down sandbox highways.
Do they see the Interstate
and dream of rolling down it?

Gleaming wheels spinning,
Churning sand furiously,
The motorcycle
Hurtles across the abyss
Carved just now by my shovel.