We did a somewhat similar road trip this past summer (August) with our family of 5 (included 3 girls aged 13, 11 and 8) and a mother in law who joined us for our last week. For perspective, our itinerary went like this:
Day 1: arrive in LA
Day 2-3: Marina Del Rey/Santa Monica Pier/Venice Beach/Beach days
Day 4-9: Disneyland (yep, 5 full days - we loved not having to rush through everything and it gave as 2 days per park plus one extra day lounge around our Disneyland hotel)
Day 10: drive to Las Vegas
Day 11: Las Vegas (saw a Cirque Du Soleil show Mystere at night and kids loved it)
Day 12: Drive to Grand Canyon
Day 13: got up early, toured Grand Canyon (there's only so much scenery kids are willing to look at) and by 1:00, headed towards Page,Arizona
Day 14: smooth river rafting in Page (kids loved it) and a Hummer tour through the desert to secret slot canyons (kids still talk about the four wheeling adventure in the Hummer!)
Day 15: drove to Death Valley and stayed in the Valley overnight (kids thought it was amazing to stay in a place where it was 126 degrees! - no worries though, our hotel room was air conditioned)
Day 16: Drove to Yosemite through Tioga Pass - awesome scenery!
Day 17: Yosemite Valley (horseback riding in the am - kids loved it)
Day 18: Drove to SF - met up with MIL who flew out that day - visited Fishermans Wharf, etc
Day 19: SF - double decker bus tour (our kids love these tours on the buses- we've done it in NYC too), Lombard St, GG bridge, etc
Day 20: Drove to Monterey (stopped in Santa Cruz and had lunch on the boardwalk) - visited the aquarium once we arrived in Monterey (mind you, this was a quick tour - maybe spent 3 hrs at aquarium)
Day 21: went sea kayaking in Monterey - kids loved this - even 75 yr old mother in law did it - got to get up close to seals, otters, sea lions - definitely one of their highlights) - got in car about 2:00 and drove straight through to Hollywood - this was a long drive along CA1 the whole way and we stopped along the way to take pictures - got into Hollywood about 11pm that night
Day 22: Warner Bros Tour - if your kids love Harry Potter, there is a lot of movie memoriabilia and a museum - you can have the sorting hat put on your head and it really talks - kids loved this
Day 23: We had ordered tickets online to see the taping of two Disney shows (Jesse and Austin & Ally) but both got cancelled at the last minute, so we ended up with tickets to see the taping of Abby's Ultimate Dance Competition (like a So You Think You Can Dance for kids) - this was totally a highlight for my kids as well because they felt like they really saw what Hollywood was all about
So..... here is my advice:
1) everyone has different preferences, but I highlighted above the activities that really had my kids excited - just thought I would throw them out there even though some are not on your route, but maybe you'd consider them
2) Yosemite in August was extremely hot and EXTREMELY busy. Mind you, we stayed right in Curry Village in the valley, but it really took away from enjoying nature when it was so crowded, bumper to bumper cars on the road, etc - we had had enough after 1 day
3) our route was a lot of driving - I think we put about 3000 miles on our rental vehicle - but our kids are really good travellers - we brought portable video game players and a portable DVD player with about 25 movies that they hadn't seen before (2nd hand store is great to get these cheaply)
4) even with your shorter route, I HIGHLY recommend getting a large premium SUV. We rented from Alamo and it was a GMC Yukon. I seriously questioned spending the extra $$ vs a minivan (the 3 weeks cost us about $2100 - unlimited mileage vs $1200 for a minivan) but my husband was concerned about having a loaded vehicle going through the August heat and the changes in elevation and how the vehicle would handle it. This SUV was a dream - it was so spacious for all of us and all our stuff for 3 weeks (and we don't pack lightly
) and there were several times when we were driving where we passed signs that said "avoid engine overheating - turn off A/C for next 40 miles) which we never had to do and we passed plenty of vehicles on the side of the road overheated - in my mind, this decision to upgrade to the premium was totally worth the money
5) Disneyland in 2 days would be rushed. The parks are smaller in area but the Disneyland park has more rides than MK in Florida and the California Adventure park now has Carsland. We stayed at the Disneyland Hotel which at the time, were allowing early entry every day for hotel guests (I think it was because of the new opening of Carsland, so not sure if that will be true next summer) and although that meant the parks opened at 7am for us, we were troopers and showed up at 7am every day (just a quick 5 min walk from our hotel) and totally had the park to ourselves for many hours. It was well worth the $$ to stay on Disney property for that perk. Rides that had 90 min waits later were ones that we just walked on multiple times in the early morning.
6) one full day of touring in SF is enough - but again, it's a personal preference - we didn't do the Alcatraz tour so maybe that would require more time -
