Do the road with magnetic paint and add magnets to the cars. Playroom or little boy's room. I think the better idea would be to place this on the floor rather than teaching kids to drive cars on the walls.
Favorite Part of this is to make a stepping stone path. HOW: cup salt, cup flour, cup (give or take) water. Knead until dough forms. Make impression. Bake at 200 for 3 hours. Do every summer and make a stepping stone path :) What a cute idea!