We took 3 full size bags for a family of 3, 16 days. Was only going to be 2 bags, but it would of meant crushing DD's Belle ball gown and hoop - yes she did the full princess thing. The gown ended up having a bag to itself, and everything else fitted very easily in the other two bags with room to spare. We then purchased two more suitcases from Target for all the stuff we purchased, and the gown got a bit squashed on the way home!
Assuming where you stay will have washing, make sure you get there early in the morning or before everyone gets back from their site seeing. I took a book/brochures, etc with me, stayed in the laundry and enjoyed an hour or so of time-out

I think I used laundry rooms twice, and handwashed a couple of times.
We took an extra change of clothes including underwear each (two for DD) in our carryon, and we changed in LAX.
When packing think of what you can wash together. For example, if you separate as much as I do, another story, make sure that all the clothes are based on colour groups, eg, not just one red t-shirt that has to be washed alone or a stray white t-shirt. But lots of blues and greens to be washed together, or red/pink/yellows etc.
As I was the chief packer, including for DH, I made a grid up saying stating what we were doing each day and what we would wear. I tried to reuse as much as possible, based upon washing facilities. Then I could make sure we didn't have too much or too little. I also learnt to handwash which was handy in LV where hotels generally don't have washing facilities.
Ooh, and remember to multibag your clothes. For example, underwear and t-shirts for each person split between bags, just incase a bag goes missing then you're not as stranded.
I also found out that water in LA/Anaheim is harder than Sydney water. So that means sometimes a bit more washing powder, or shampoo in your hair for that mater. I purchased Tide washing powder when we were there but I would of much rathered what I was used to. Perhaps pack a small box of Omo or whatever and triple pack in ziplock bags!!!