Get the kids some skateboarding lessons from GoSkate.com. This site will basically hook your kids up with a skateboarding instructor in your area. They have instructors all over, so you don't have to be in California to use this service.
If you find an instructor that you like, you can ask them to come to specific spot that you like. For example, if they kids are just looking to get basic skateboarding lessons, all you need is a flat area. If you know a road that has just been paved and is not busy at all, that might be a good spot.
Usually I would say take the lessons with the kids. But if the kids aren't taking longboarding lessons, bring a lawn chair, a camera, and a fruity drink and watch the wee ones.