“Eat me on the moon!”
S'mores are the perfect thing to make with your kids. Send them out to scout out a house in the neighborhood that just had a cookout in their backyard, with a barbecue grill still warm but not cool. Hand out graham cracker squares, milk chocolate squares and large marshmallows. Explain to them to go back and make sandwiches of these ingredients and to be careful not to burn them, but to heat them just enough to melt the marshmallows and chocolate slightly. Also explain that they should run back to you with the finished s'mores as fast as possible, with the winner getting a prize. That prize would be one of the s'mores they made, with you getting the rest. Just in case one of your kids comes running back on fire, keep an extinguisher handy.
In addition, do not explain to the kids that graham crackers, chocolate and marshmallows cost money, the money you swiped from their piggy banks. They will be happier with their accomplishments if you leave out that part.