You don't mention when your trip is, so I don't know if this is too late...but having made the same trip twice with kids around the same ages, I can offer lots of advice if it is still pertinent. We took us1 down and returned up the middle.
Disneyland: the block(s) around Disney are full of hotels, motels & budget family restaurants. We have stayed several times at the Castle Inn. It CHEAP (less than $100/ night) and more importantly, directly across the street from Disney's main gate. The rooms are very plain, but functional- but you will not be spending much time in the room. You will likely be at Disney until your kids keel over from excitement and/or exhaustion. They have a pool and "cute" gargoys around the place as well as fake turrets- it appeals much to kids. They are not full service, but there are lots of places to eat in that neighborhood.
Don't plan on doing anything else in the time you have allocated to Disney- it just won't happen.
At Disney, get the turkey legs for lunch: healthiest food available in the park & a huge portion for just a couple of dollars (no doubt your kids will get their share of sugar along the way).
We personally prefer Legoland, especially with younger kids- (it's less crowded and the rides are more appropriately sized) BUT it is not very much different from Legoland Windsor- so is likely not worth the extra drive time for you (although san diego is a wonderful town and a great place to go with kids).
Along the route: we stayed in big sur and had a wonderful time: beautiful place. We got a terriffic rate on a cottage through the Entertainment book- paid something like $50-60/ night for a huge 2 bedroom cabin. Rates and deals vary, but you can literally get rooms for half price or better through the book, so it's worth buying one (and they are now available at half price, or around $20...they discount the books midway into the year).
There are also great places to stay in sequioa park, but you need to book in advance! If your kids get car sick (one of ours did) or have vertigo...avoid sequioa.
If you haven't already completed your trip and would like more information on the things I mentioned, or more tips, post or PM.
Aloha,
Elise