>>10737771G.I. Joe doesn't really play well with 5 year olds. Too many tiny parts and fragile figures. You're better off getting True Heroes or other discount military figures. They usually have solid figures, large accessories and some very sturdy vehicles.
The figures won't have the detail or articulation of a Joe, but they'll survive rough play and toy box burials much better. And they're still fun toys, even for older fans to collect.