Excellent article on the home page of this site: "Hiking with Children" by Penny S. Click on the title in the left-hand column under "Experiences."

You'll soon find that except on paved paths, the stroller or wagon will not work--you'll need a kid carrier for the youngest so you can carry him/her on your back. However, the paved paths are a good place to start. Expect lots of frequent stops to examine bugs, worms, butterflies, etc., or "energy breaks" (i.e., snacks).