Yay! I like getting advice from people who think like me.
Since it's 4th of July week, would it make a difference which park I go to on Sunday. For instance, since Cars will be the big attraction, should we go to Disneyland on Sunday and try DCA on Monday?
I have no strategy yet, but that sounds like a smart plan. And if you have park hoppers it's so much easier to go to the other park than it is at WDW if you change your mind. They are literally right across the courtyard, no need to get in a vehicle at all and lose park time.
Also, I have no idea of scope. Is DCA about the size of DHS or is it bigger?
You know, I'm not sure. They feel about the same size, but DCA is laid out better. I feel like I have to backtrack at DHS to get in and out of certain areas, it seems very closed in. DCA seemed much more open to me last time I was there.
How different are ToT and TSMM from WDW?
ToT is different. DCAs only goes up and down, it doesn't move forward into the corridor like the one at DHS. I think it's the only ride that is better at WDW than at DLR. I don't know about TSMM as I haven't been on it in CA.
I like the idea of the Paradise Pier stuff, but don't think my DD6 will have anything to do with the roller coasters and the rest of it looks like standard fair rides, so maybe not must-dos. Is that accurate?
I think so. I'm not a fan of the ferris wheel, and we didn't spend much time at Paradise Pier when we were there in 2010, although we really liked the swings, not sure what they're called now. I may spend some time there on my own in May, I'll let you know if my opinion changes then.
For Disneyland, my list is longer: all of Fantasyland, Indiana Jones, PotC, HM,and the submarines for sure. Will I be able to do all that? I read somewhere that the average guest gets on 8-9 attractions a day.

That seems really low. I definitely want to soak of the atmosphere and enjoy the original, but I want to be able to do the things the girls have never done.
Start early and utilize fastpasses. The return time isn't being enforced yet at DLR as it is at WDW, so you can make the most out of the FPs. I think you'll be able to get all of those in.
The rides that I feel are can't miss are:
*PoTC (twice as long as the one at WDW, and the bayou is awesome)
*Space Mountain (if you like roller coasters, way smoother and all around better than at WDW)
*Indiana Jones (same ride vehicles as Dinosaur, but so much better)
*Storybook Land Canal Boats (relaxing quiet ride, but so cute, one of our favorites and doesn't exist at WDW)
*Peter Pan (no explanation needed)
*Grizzly River Run (similar to Kali Rapids, but without the clear cutting)
*IASM (Far and away better than at WDW)
*Matterhorn (will be opening again a couple of weeks before we get there, loved the old one, hopefully the new bobsleds will be more awesome)
One more thing, is it possible to do Fantasmic and the fireworks on the same night? What is the best strategy for nighttime shows?
Sorry, no answer for you on that one, I have yet to see Fantasmic. I know it's possible to see WoC and the fireworks on the same night, but I would hate to make assumptions.
We try to do 5 days each trip and spend one day in each land at Disneyland and one day at DCA. Of course if we get through one land early in the day we go back to stuff we want to do twice or move on to the next land.
Have a great trip, maybe I'll see you there.