Hi all, thank you for your valued input which has all been noted. I have made some changes to the itinerary based on your feedback and I post this below for your thoughts. I have to say that I am disappointed to miss out on the second day in Death Valley (my favourite place!) as well as not getting to walk on the Skywalk (something I've wanted to do since I first heard about it years ago!) but this isn't 'my' trip and I think it will ultimately make for a better trip which is hopefully more appealing to our two youngest travellers (yes, AZBuck, there are now a couple of kids along for the ride - well, not that young now, at 12 and 11 years!)
I am aware that there is probably a couple of days where the amount of driving is less than perfect and I'd really have liked an extra day to stretch the drive back from Grand Canyon but it is what it is and hopefully, as Rick says above, the kids will be used to the road life by that stage! I agree about Lake Havasu but, well, it's part of the colour of the road and the story of the bridge which moved from 20 minutes down the road from where we live is too good to pass up!
So here is the revised plan; any further suggestions or thoughts very welcome! As above particularly with regard the parks at Channel Islands, Pinnacles and Joshua Tree.
Tues 8th - Day 1
Fly London – Los Angeles
Collect rental car
Stop for food eg In and Out Burger or Chick-fil-A
Overnight accommodation booked: Tilt Hotel, Universal City
Weds 9th - Day 2
Relaxing morning settling in
Visit Hollywood sign from Griffith Observatory or Mulholland Drive?
Old LA Zoo in Griffith Park?
Burger King in Burbank (BTTF)?
Movie locations?
Overnight accommodation booked: Tilt Hotel, Universal City
Thurs 10th - Day 3
Universal Studios
Overnight accommodation booked: Tilt Hotel, Universal City
Fri 11th - Day 4
Universal Studios
Overnight accommodation booked: Tilt Hotel, Universal City
Sat 12th – Day 5
Leave hotel and drive down to Santa Monica
After lunch follow coast road to Ventura
Overnight in Ventura area (not booked)
Sun 13th - Day 6
Channel Islands cruise from Ventura – arrive back late PM
Drive to Solvang (+/- 1 hour)
Overnight in Solvang (not booked)
Mon 14th – Day 7
Continue along the coast road toward San Francisco
Pismo Beach, San Luis Obispo, Morro Bay, San Simeon (Hearst Castle/Elephant Seal viewing spot), Turn around at Ragged Point
Overnight outside Pinnacles NP (Soledad or King City) (not booked)
Tues 15th - Day 8
Visit Pinnacles NP
Drive to Monterey (+/- 1.5 hours)
Take it easy for remainder of day
Overnight in Monterey or Carmel by the Sea (not booked)
Weds 16th - Day 9
Whale Watching AM
Drive south to Big Sur area
Overnight in Monterey or Carmel by the Sea (not booked)
Thurs 17th - Day 10
Leave early and drive to San Francisco via 17 Mile Drive (+/- 3 hours)
Golden Gate bridge viewpoint
Baker Beach
Fishermans Wharf
Lombard Street
Alcatraz Island
Cable cars
Overnight accommodation booked: Hotel Caza San Francisco
Fri 18th - Day 11
San Francisco
Overnight accommodation booked: Hotel Caza San Francisco
Sat 19th - Day 12
Drive to South Entrance of Yosemite National Park (+/- 4 hours)
6pm Moonlight train ride on Yosemite Mountain Narrow Gauge Railway
Overnight accommodation booked: Narrow Gauge Inn
Sun 20th - Day 13
Mariposa Grove hike (+/- 2 hours)
Explore west of Yosemite (Washburn Point, Glacier Point, etc.) then head in to the valley
Overnight accommodation booked: Curry Village (check in 4pm)
Mon 21st - Day 14
Yosemite Valley
Yosemite Falls
Half Dome
Leave Park via Tioga Pass
Mid afternoon stop at Bodie State Park (closes 6pm)
Overnight accommodation booked: Virginia Settlement
Tues 22nd - Day 15
Drive in to Death Valley National Park (+/- 4 hours)
Mesquite Flat Sand Dunes
Badwater Basin / Devils Golf Course
Artists Drive / Artists Pallette
Sunset Zabriskie Point
Swimming pool at Ranch after dark
Overnight accommodation booked: Furnace Creek Ranch Cabin
Weds 23rd - Day 16
Sunrise Dantes View (leave hotel at 430am)
Drive to Grand Canyon National Park (+/- 6.5 hours)
Pass Las Vegas and stop for quick visit to Hoover Dam
Sunset time approx 7pm
Overnight accommodation booked: Yavapai Lodge
Thurs 24th - Day 17
Sunrise time approx 6am
Explore Grand Canyon National Park using shuttle buses
Drive back to Kingman (+/- 2.5 hours)
Overnight Kingman (not booked)
Fri 25th - Day 18
Drive to Joshua Tree National Park (+/- 3 hours)
Roadside attraction: London Bridge at Lake Havasu City
Explore Joshua Tree National Park
Drive back towards LA and stop at San Bernadino (+/- 2 hours)
Roadside attraction: World’s Biggest Dinosaurs at Cabazon
Overnight Wigwam Motel San Bernadino (not booked)
Sat 26th - Day 19
Drive back to Six Flags area (+/- 2 hours)
Anything outstanding to north or west of Los Angeles
Stock up with Prime!
Overnight near Six Flags (not booked)
Sun 27th - Day 20
Full day in Six Flags
Overnight near Six Flags (not booked)
Mon 28th - Day 21
Fly Los Angeles - London