Rc Car exhibit, for kids science museum.

Calling RC-monster heads, a local musuem for kids is wanting my advice on building an rc car exhibit that can last the test of repeated use by children.
Please Help us with your advice about a challenge of building a high volume use extreme rc car exhibit. They have very little space, 4 X 8 maybe a bit larger (i know this is really micro). One of the difficult things to advise on would be which car, which scale (either 1/18, 1/24, or 1/32). They would have to be geared or programmed to have very little speed. Since bus loads of kids will be using the cars, durability is very important. Ease of Maintance is also important. thanks for any and all input

idea so far (feel free to critique)

Lexan enclosed area (so kids can't handle cars, or track).

vehicles might use associated 18r, losi micro SC, Losi Micro Crawler