P.S. In the U.S. it gets dark about 7:30-8:00pm that time of year, so you can still get some good driving in if you leave Yosemite around 4:30-5.

First things first: Try to book lodging for Yosemite and Grand Canyon first, as the most convenient lodging (inside the parks) will completely enhance your visits. You really will need two nights in Yosemite.

* Keep your 3 nights in San Francisco. You can enjoy SF while recovering from jet-lag.
* Book 2 nights in Yosemite. If you are unable to get in-park lodging, ask us again for alternatives for lodging. You really will need 2 nights in Yosemite.
* Yes, you will most likely need to spend a night between Yosemite and Grand Canyon, but don't worry about that for now.
* Try to book lodging for Grand Canyon inside the park.
* The national park lodging usually has a 48-hour cancellation requirement, so reserve something now. You can change it a bit later if needed.

* Check Google Maps or Mapquest for directions and drive times between your destinations and decide if you want to spend that much time in the car.

* You will need one day each for Disneyland and Universal Studios.

If you don't like using so much time for driving to Grand Canyon , you might decide to drop GC from your itinerary. Or drop Yosemite. If the long, full-day drives are not bothersome, then go ahead with your plans.

thank you all, certainly given me something to think about, I'll let you know what we end up doing!
PS what tours do you suggest in GC?

No tours necessary. Just park along the rim to get the views. You can also walk down one of the trials to the first spring without any problems.

http://www.flickr.com/photos/mksfca/...57622644716819

There is a great bus shuttle system in the Grand Canyon - and you catch it in front of the Lodges that are on the rim. I would recommend you check out Bright Angel as a starting point, and try to get room with the Canyon view. You can also walk along the rim from there. http://www.usparklodging.com/grandca...FQ1jhwod8EOyYg

Your prospective road trip is ambitious - but very doable in my opinion, if you like to drive and see the country, as I do. You can also drive from Yo - up and over the Tioga pass - and down 395 and then over/through Death Valley on your way to Las Vegas. Start early - maybe have breakfast at beautiful Tuolumne Meadows http://tinyurl.com/7wxopld and then on your way. From there - it's what - 5 hours to the GC?

And yes, if you are returning to LA from Las Vegas on a Sunday (4 plus hours normal drive)- do leave Vegas early (as suggested - before 9 AM if possible) - and maybe coffee up/have a snack in Baker - about an hour and a half from Vegas. http://www.travelmath.com/drive-dist...V/to/Baker,+CA

While I agree with everyone on here that the best way to see Yosemite is to stay inside the park for 2 days if possible, it seems to me that doesn't allow your teenagers to enjoy the amusement parks that you want to go to in LA. Here is the plan I would suggest which will give you 2 full days in LA:
8, 9, 10 - San Francisco
11 - Yosemite
12 - somewhere in between (I would go farther than Lone Pine though)
13, 14 - Grand Canyon
15 Las Vegas
16, 17, 18 - LA
19 - home

You can return the car in Anaheim and stay in a hotel that has a package deal with Universal and Disneyland including transportation. See http://www.cityescapes.com/us.asp?id=5

One day in Yosemite (actually a bit over 1/2 a day when one factors in the drive time) - but 2 days at the Grand Canyon? That really doesn't make sense IMO. There is MUCH more for teenagers to do in Yosemite than at the GC.

If you are keeping the GC in your plans (I note you are wondering whether to drop the GC) - 1 night 1+ day is enough. W/o the hike, the GC is mainly the view and one full day is plenty.