My 2.5 year old Isabela has been camping with us since she was 6 Weeks old. Now she absolutely loves it. (She has been begging me all Winter.) It took me, Mr. Ultralight, a while to get used to all the gear that is needed with kids, but it's been well worth it.

At about 18 months, we started activities while camping. She LOVES track and scat identification. She can pick out deer tracks and scat from 15 feet away.

We also got her a toddler's digital camera. Low res, crappy pics, but she feels like an explorer with it. We have gotten a few kids books too that have trees, insects, tracks, and flower identification. That keeps her interested too. Not as much as poop though...
It's not an easy undertaking, but I'm glad to be sharing my experience and knowledge with the kids, and hope that they someday appreciate the outdoors.