I agree with using snacks/trail food for day hikes. We take raw veggies, dried fruit, jerky, cheese, meat stick, etc. I carry a small esbit stove and a stainless cup if I take a bag of freeze dried stuff with us.

I always carry 2 qts of liquid (water/gateraid) and the wife carries 1.5 qts. plus water purification tabs if we need more.

I would also suggest having a small light for each person, just in case. Having the kids at least carry some of their own food/water/clothing will give them a much greater sense of ownership and give them something to do as well.