If you are booking right at 7 months and the first night is not available, it will not let you book subsequent nights. You have to wait until you are 7 months out from the first available night
to secure any reservations.
I would suggest entering the waitlist immediately for all nights. Then you could return the next day and try to secure available nights and adjust the waitlist.
As for crowds, it stands to reason that summer weekends would be busier. As for the degree, I'm not enough of an expert to comment on that. We've taken 5 or 6 trips to Disneyland now and I've always found it pretty easy to hit everything with sensible touring plans (get out early, use FASTPASS, etc.)
Your biggest challenge will be touring both parks in just 2 days. There may only be two parks at DL but if you really do a side-by-side list, there are nearly as many attractions in those two parks as in all 4 at WDW. Disneyland doesn't have anything to compare to Epcot's World Showcase or Animal Kingdom's savanna but Disneyland's two parks are much more heavily populated than the four at WDW.
Our last stay at the Grand Californian was 6 nights and we STILL didn't see everything. Kids were keeping count.
If two days is all your time / budget will allow, you can do a reasonable job of seeing the parks. But there's little chance of seeing everything--weekend or not. And if you do try to do as much as possible in 2 days, you'll spend so much time running from attraction-to-attraction that you won't have much time to enjoy the experience.