Probably the best advice that could be given, is when you do take them afield and they start loosing intrest while hunting, stop hunting. Whether you are deer hunting or tukey hunting, etc., if they are ready to go home or do something else then stop. If you force them to stay in the woods and they are not enjoying it, they'll remember that the next time you want them to go and choose to stay home! It has to be fun for them when they are young.
Ditto on that.
Just remember a childs attention span is not the same as yours and as long as you make it fun then they will want to keep going with you.
Try doing a spot and stalk on pigs with them that way they will always be doing something and not just sitting in a blind where boredom will quickly set in and we all know what kids are like when they are bored