Normally I would say that it should be manageable, even it is the first weekend of the holiday season, but the Avengers Half Marathon makes it hard to guess what crowds will be like. It's the first time
Disneyland has had a marathon that coincides with the official start of the holidays. My instinctive answer is that the parks will be busy Fri to Sun due to the combined marathon and start of the holiday season,
but as long as you go expecting crowds, it'll probably be okay. If you go expecting super low crowds, walk on rides, and getting to the parade and fireworks just a few minutes before they start, then I think you'll be disappointed. So plan on crowds and then you'll be prepared.
Based on the calendar, it looks like Fireworks and the Christmas Parade will both be presented on Sunday and Monday, so you have that flexibility in days. Mad T Party (in DCA) is only offered Fri to Sun, so if you wanted to see that and weren't planning on being in DCA on Fri or Sat, you'd need to go on Sunday to DCA. The parks do close early on Mon, and they also open later (10:00 am compared to 9:00 am) on Monday. So, if you're morning people, then you might consider going on Sunday to take advantage of the hour earlier that the parks open.
In terms of park days, I tend to start at whichever park is not having EMH/MM, but that primarily pertains to my DCA day. I like to go to DCA at (or before) opening and then head straight to TSMM at opening. It does not have FPs and the line tends to build and stay long throughout the day (not quite DHS-long, but still long enough). Then I get a RSR FP. So looking at the calendar for your days, I would probably plan to start Saturday in DCA (given that you're going to DL on Thursday). My plans also tend to do a fair amount of park hopping because the two parks are only 110 yards apart. So it's very easy to park hop (think of it like going from Future World to World Showcase in Epcot).
In terms of parking at DTD, I've always been told you can get your receipt validated at any of the TS locations (I've done this at Brennan's Jazz Kitchen) and/or if you watch a movie at the AMC theater. I've read reports that the QS locations (like Jazz Kitchen Express) cannot validate receipts (I haven't tried).