My Son Morgan and I go geocaching most weekends, he is 7 years old and absolutely loves it and it should be said that I do too!!. Its also a great excuse/motivator for getting out in the countryside. I have always invested in good gear for my son so that no matter what the weather we can go out geocaching/hillwalking, but bear in mind the premise of the whole thing.............
Primarily I am persuading my son that the great outdoors is the place to be, instead of street corners drinking and smoking, so the incentive of an adventure with a reward at the end of your labours makes it a no brainer and he is eager to get out. We have also placed a few caches too and this gives the same amount of pleasure as he can track the visitos and see how popular his caches are. All said it is a great passtime and one we enjoy very much, so my advice would be give it a go, see what you think.
Regards
Lee