The wheels come with tires? If yes...
Get some free cardboard from any retail store, cut out round circles 1" bigger than the size of your wheels, for both sides of the wheel. Fill the inside of the wheel with newspaper to give the 'back' cardboard side some support. Buy some shrink/stretch wrap on a roll (10bux) and wrap the entire wheel and tire.
If the wheels come without tires. I'd still do the same thing, but wrap the outside of the wheels (edges) with a buttload of bubblewrap. Play it safe.
-j
