I have had excellent times with my two boys bowhunting. (They are 10 and 13 now, but have been out in the woods with me as early as age 9.) The key is not to push them too hard and burn them out at an early age. This may mean hunting for shorter periods of time to match their attention span. Warm Fall weather is usually the bane of bowhunters, but it is good to take the kids out in. If you take them when it is really cold they may grow to hate it trying to hold still and stay warm while you are hunting.
I have had them climb ladder sticks with no trouble. I'll either put two stands next to each other on the tree trunk or hang a stand right next to where I have a ladder stand set up.
Be sure to belt them in well. My boys have also gotten a big kick out of rattling antlers. My younger son called in two bucks last year in one afternoon and his eyes were as big around as saucers. When we got down to leave later, he said that, "That was FUN!"