One of the things I love about children is their spontaneity.  The younger the child, the more of it you see.  They havn't shut down yet, thinking it's weird to act silly in public.  If you watch children do this, they're having fun!   Okay, so you're not willing to look silly in public; how about with your kids in the car?  Take truns making silly faces in the car, copying one another and having some fun.  Maybe you could even give the faces special names and use them again when your child least expects it.

The more you lighten up as a parent and begin having fun, letting your little kid within pop out to play, the more fun  you'll have with your children.  It's definitely a win-win for everyone.