Any major holiday will be a little chaotic at Disney Parks. The ride lines would be long and the park will indeed be congested. With that said, with a little planning, you can get through a few major rides and if you use fast passes, it will help.
Typically how my wife and I plan our day at DL is to head straight for Space Mountain and Star Tours when the gates open. After that, get fast passes for the rides you want to go on later in the day. Time it every hour to grab more fast passes to other rides you would like to ride. Fast passes are definitely your friend during holidays, but they sell out fast.
So choose a ride during the opening at DL and head straight there, then plan to try and get to the rides in the area you're in. It can be done.
Just know, most likely the rides or attractions you are looking forward to, others are too.
Basically here is how my wife and I run through:
1. head to space mountain and star tours, grab a fast pass to space mountain before you ride it, since they sell out fast. (If you like the ride)
2. Head over to Big Thunder Mountain Railroad, Winnie the Pooh, and if it's hot already, Splash Mountain. If it's hot, there will already be a long line for Splash Mountain. My wife and I usually skip it because it's a long line. But fast passes are available for it as well.
3. Head to Haunted Mansion then to Indiana Jones or Jungle Cruise
4. Lunch time
5. by this time the park is full and we just try to find rides we don't mind waiting for. We might go to some of the more traditional rides in Fantasy Land
6. After watching Fantasmic head to Pirates of the Caribbean (if the line isn't long), it's a great way to relax and skip the crowds migrating from Fantasmic. You might have to choose to watch Fantasmic or Fireworks show since I'm sure it will be packed.
That's basically one day. If we were going multiple days, we would follow the same routine, but switch up the rides. Same for DCA, but being that Cars Land just opened and the rest of DCA was updated, I'm sure it will be crazy.
Good luck!