If you're looking for a neat and painless way to introduce your kids (or lifelong city-dwelling friend who isn't positive that trees or flowers are real) to the animal kingdom, I suggest the transition from dinosaur pajamas and Jurassic Park marathons to the dinosaur's nearest modern relative: the bird. Even if you're not a big nature enthusiast yourself, birds are a good jumping off point because you don't really have to hang out with them so much as establish that you are not a cat who is going to eat them. "NeighBirds" (tiny groan) by Utoopic is an elegant modular birdhouse that promotes a close-knit bird community, if you so choose. The houses are easy to install almost anywhere, including branches, hooks, and walls, which means it's easy to do your part for the post-dinosaur dinosaur.
NeighBirds on Utoopic