Redneck modification to game cart

I have my young boys bicycle's tore apart,trying to rig something up with their wheels. Of course,I have bearings all over the driveway,and hub guts in the trash,but I do have inspiration. Dragging a buck and several hogs last year over 300 yards really sucked. I will succeed.

This is the exact one I have here.
http://www.sportsmansguide.com/net/cb/guide-gear-aluminum-deer-cart.aspx?a=450180
Everyone has a similar version for $59. That is what I paid 2 years ago. Best money ever spent. 3 years ago I shot a 300# hog about 1/2 mile from the truck in the last 2 minutes of light. I swore that was the last animal I would ever drag. Deer don't bother me but hogs are just too hard to drag