There is no other magical place on earth than Disneyland and it all started right here in California. Everyone should experience this wonderful land of fantasy at least once in their life. If you want to travel to California for a theme park this one should be first on the list, but there are plenty of other great ones as well.
You should try out the fairly new California Adventures which is more of a larger than life fair with great rides or try Universal Studios Hollywood, Knotts Berry Farm, Legoland California or Six Flags Magic Mountain to name just a few.
Take your pick for whatever you and the kids like the most but it might be a tough choice so you will just have to keep returning to California to visit them all!
