You can have a food table for the kids with all of favourite snacks and treats for kids and another one just for the adults, with alcohol and "adult" treats. I went to a party once where the kids got to decorate their own sugarless cupcakes while the parents had normal cupcakes with all the sugary goodness.
For fun, you can screen a movie and serve popcorn and snacks just like at the cinema or you can get one of those bouncy castles!
Saime Firmanes