I have a 4 year old and a 7 year old that will jump at the chance to go geocaching, and will even endure the longer-and-longer car rides to get there. Not only that but I now have 4 neighbors' and friends' kids that get their parents to call and see if I'll take them as well.
If I take many more kids, I'm sure I'll have to get some sort of a license!
Truly, though, their excitement makes it all worthwhile. I wish that "kid-friendly" were a formal property of any given cache we could set and query when searching for caches.