Trip review
Anyway, taking into account the inputs here (and other readings) I got so far, I'm now revising my itinerary to be like this. This now supposedly eliminate the two super-long drive that I had before.
Day #1 (Thursday) Arrival LAX 2pm, enroute to Hollywood apartment
2 (Friday) LA - California Science Center, Hollywood, Beverly Hills, etc
3 (Saturday) LA - Santa Monica, Venice
4 (Sunday) Citadel Outlet + Enroute to Anaheim
5 (Monday) Disneyland
6 (Tuesday) Enroute Anaheim to San Diego, Sea World
7 (Wednesday) USS Midway Museum + Enroute to Kingman
8 (Thursday) Enroute Kingman to Grand Canyon
9 (Friday) Grand Canyon + Enroute to Page (Antelope Canyon, Glen Canyon Dam, etc)
10 (Saturday) Enroute Page to Las Vegas
11 (Sunday) Las Vegas
12 (Monday) Enroute LV to Bishop via Death Valley. Overnight in Bishop.
13 (Tuesday) Enroute Bishop to Yosemite via Tioga Pass
14 (Wednesday) Yosemite whole day
15 (Thursday) Enroute Yosemite to Carmel Valley, Monterey. Overnight in Monterey
16 (Friday) Enroute to SF via Silicon Valley area
17 (Saturday) SF - Golden Gate Bridge + Park + California Academy of Sciences
18 (Sunday) Exploratorium + Fisherman Wharf + Pier-39, etc
19 (Monday) Spare time morning. Night flight back to SG
Accommodation wise, I already have candidates (and some already booked) in all the places, EXCEPT for SF! It seems almost mission impossible to get a place for 5, with rather good review, not too far from the places I want to visit above, with budget of less than USD 300 per night
Coming back here to thank everybody who gave your inputs few months ago, such that our trip in June has completed successfully. Special mention for Shiny Things, Patryn33, etc.. for lots of inputs, thanks!
I thought let me give back by sharing back a bit on our trip:
Day #1 (Thursday) Arrival LAX 2pm, enroute to Hollywood apartment
-> Took UberXL from LAX, it's really good value for money (vs taxi or shuttles), as our family is 5 pax.
2 (Friday) LA - California Science Center, Hollywood, Beverly Hills, etc
-> Enjoyed our time in CSC, watched the 3D Imax and saw the Endeavour space shuttle.
3 (Saturday) LA - Santa Monica, Venice
-> We went to Original Farmers Market in the morning (quite enjoyable for the food + souvenirs), then Santa Monica beach in the afternoon. Unfortunately it was quite cold that day, so didn't go into the water.
4 (Sunday) Citadel Outlet + Enroute to Anaheim
-> The only day dedicated for wifie to do shopping

I found that not everything there was cheap. What we found cheap there: Coach & Kate Spade (really big difference vs SG price), GAP, Carters. What's NOT cheap there: luggages (including Samsonite), Crocs, Clarks, Ecco,... Seems better to buy online for these. Or maybe we simply were not at the right time for sale.
5 (Monday) Disneyland
-> We stayed right opposite the entrance, hence enabling us to go in early (8am), got out for lunch and nap in hotel for the kids, and then go back in the afternoon to continue playing until close time (11pm). We felt that it's the right decision, especially seeing the traffic jam outside Disney around closing time.
6 (Tuesday) Enroute Anaheim to San Diego, Sea World
-> Sea World is not exciting as we hoped. The main highlight (Shamu Show) is pretty much "whale splashing water to audience" show

In fact what we loved was La Jolla Cove, which was slightly outside San Diego.
7 (Wednesday) USS Midway Museum + Enroute to Kingman
-> USS Midway was definitely interesting for airplane lovers. We then proceeded towards Grand Canyon via Prescott Valley (instead of Kingman). It was a really long journey (made worse by fire in one of the town which forced us to turn back and went a big round). However our hotel (Hampton Inn at Prescott Valley) was very pleasant. Probably among the best across all our accommodation in this trip, while being the cheapest at the same time.
8 (Thursday) Enroute Prescott Valley to Grand Canyon
-> Main highlight was the sightseeing by the Grand Canyon free shuttle bus.
9 (Friday) Grand Canyon + Enroute to Page (Antelope Canyon, Glen Canyon Dam, etc)
-> We had breakfast at the famous El Tovar restaurant. Frankly we felt that it's over-rated

Antelope Canyon was really beautiful (do take the noon time tour, it's worth to pay the extra price for the noon sun beam!). Glen Canyon Dam tour was interesting as well.
10 (Saturday) Enroute Page to Las Vegas
-> Nothing particularly interesting on this day. We had wanted to watch the Mac King Show but failed to arrive Las Vegas in time for the show. Not much other choice for family-friendly show in Las Vegas.
11 (Sunday) Las Vegas
12 (Monday) Enroute LV to Bishop via Death Valley. Overnight in Bishop.
-> Another long drive day. We enjoyed Death Valley's unique scenery. The journey was quite taxing for the car (especially Dante's View), make sure your car is fit for the long climb. We loved our hotel in Bishop (Creekside Inn), it's a really lovely place.
13 (Tuesday) Enroute Bishop to Yosemite via Tioga Pass
-> This is probably THE BEST part of the whole trip. There were many places with partially melted ice on the road side of the Tioga Road, so the scenery was really amazing, and the kids got to play with snow at the road side too. Definitely highly recommended to pass this road.
14 (Wednesday) Yosemite whole day
-> We took the valley floor tram tour, which allowed us to conveniently see all the highlights of the Yosemite valley. Note if you ever get accommodation in the tent of Half Dome Village (used to be Curry Village): it can be bloody cold even in summer! We experienced 2 celcius at night, and obviously couldn't really sleep properly in the tent (despite 3 layers of clothing + 2 layers of blanket). But it was a fun experience

15 (Thursday) Enroute Yosemite to Carmel Valley, Monterey. Overnight in Monterey
-> I think Monterey was under-whelming. The 17-mile drive was not impressive either. I wouldn't really recommend it.
16 (Friday) Enroute to SF via Silicon Valley area
-> We drove into the complex of Apple, Google, Facebook, etc. Apple and Google has merchandise stores to buy some unique souvenirs. The Apple ones, as usual, are over-priced (more expensive) compared to Google's

*Apple fans don't kill me

17 (Saturday) SF - Golden Gate Bridge + Park + California Academy of Sciences
18 (Sunday) Exploratorium + Fisherman Wharf + Pier-39, etc
-> We shifted these places to Day-19. On Day-18, we went to Muir Woods instead. Quite an interesting place to visit, BUT do go early (i.e. arrive by 9am max), because the carpark is really limited. We also went to Bay Area Discovery Museum, which is perfect for kids up to 5-6 years old.
19 (Monday) Spare time morning. Night flight back to SG
Hope this is useful for anyone planning to visit similar places with us. The almost 4,000 km road trip was a really epic (though tiring) journey
