Good question. You can get a tire back on the rim with one of two methods: lubrication and muscle power or fire.
For the lubrication method, you will need the tire, the rim, some dish detergent, and a pry bar. Flat ground is also essential. This is probably the safer of the two techniques, given that it sounds like your nephew will be participating.
For the dangerous fire method, you will need the tire, the rim, some WD-40 or starter fluid, a lighter, and a fire extinguisher.