that's great, moments like that will keep them thinking of the fun you had together while you're away. my wife, 2 year old daughter and i stayed near fort sill on my pass, and there was a place where water shot out of the ground randomly, my daughter had a blast and i can vividly picture her laughing every time one would shoot up and surprise her. i wouldn't trade that one memory for all the squerrils and deer in the world!
way to get your son involved! good job dad.