The crowd levels are usually very nice and low that time of year but unfortunately, that means Disneyland uses that opportunity to close down lots & do most major refurbs. The last 4 years we have always seen Splash & GRR down from mid-Jan to mid-Feb at the very least. One year we even saw all of Grizzly Peak closed at the same time & another year all of Critter Country during that time. In 2015 when they were getting ready for the Diamond Celebration it seemed like so much of both parks was down at that time: castle was scaffold-ed, Matterhorn was down for a lengthy refurbishment in addition to Splash & all of Grizzly Peak with GRR & Soarin’ & Peter Pan was about to be down for a lengthy refurb. We went right before Peter Pan closed down fto make sure we saw it one last time before any drastic changes.
The best bit of encouragement I can give is that I feel like Feb 2016 had a quite a bit more closed down including Autopia, Pirates, Jungle Cruise, IASW for removal of the holiday overlay plus the Railroad & all Rivers of America attractions were still down. So a lot of ‘people-eater’ type attractions. So I know that for 2018 it might feel like more of your favorites will be down but overall there should be more capacity for attractions to be absorb people which will make your wait times more enjoyable. In my 4 years of avidly paying attention & pretty frequent visits to DLR, I’ve never seen Dumbo down so that one is new. My hunch is that because it has been some time it will be a longer one. But hopefully it just doesn’t require a ton of maintenance and they are able to have it back up by your early Feb dates.
I’m also super bummed about Screamin’ as my son is in the same boat being still too short (by less than an inch with shoes though) & we aren’t going back before Jan 8th to try for one last time to see if he is tall enough. Everyone keeps telling me that the ride will still be the same ride, just a new theme/new music etc. so maybe you can help her avoid being sad by encouraging her that next trip for sure she will be tall enough & it shouldn’t be down (I don’t think it’s ever been down for refurbishment since it opened, of if so very very short refurbs). She might even like the Incredibles theme better than its current theme (which I suspect most kids will).