The newest park at Disneyland is the California Adventure park; it's a lot of fun! There are a lot of great rides for older kids but the little ones aren't left out! Plus it's a 5 minute walk between parks; rather easy to park hop depending on your mood.
The area of the park designated for the film "A Bug's Life" is a great for the younger kids, a lot of small rides that won't freak them out and areas for them to just run around and burn off the excess energy from riding in a stroller all day!
One of the biggest differences between California Adventure and Disneyland is a lot of the rides are targeted to the older kids and adults-- Tower of Terror comes quickly to mind. There is a lot to do here as well, the pier with all sorts of rides and arcade games, the restaurants, the activity parks-- just strolling through it is pleasant.
One of the best rides ever, so popular that they built a copy in Florida, is "Soaring over California" that is an amazing ride, not scary at all but does get all the senses involved; sight, smell, touch, hearing totally worth the long wait.
Don't gloss over this park, it deserves it's own dedicated days to fully see and do everything there! Don't forget to go on the river ride, but make it your last ride of the day as you will get SOAKED!