Hey there...
We've gone the past 8/9 years and will be going back to Disney for our ninth Christmas this year. We usually go from 12/24-1/1.
Alright, so this year can and will be different due to free dining, but here's what you'll typically see as far as crowds (1 being the lowest, 10 being the highest). Remember, this is comparatively speaking. A Christmas "7" is higher than an everyday 7 you'll find on Touring Plans.
12/23: 7; this is a Sunday and will be a check-in day. Most people who come for the "week before Xmas" will leave on 12/22 and head home for the holidays. Many people taking advantage of the free dining discount will check in on this day.
12/24: 8; Obviously it'll be crowded on this day. Can't speak for the parks because we always check-in and hang by the pool. A lot of people who didn't get free dining will check in on this day.
12/25: 10; High crowds. MK will hit a Phase 3 closure; Long waits, wall-to-wall crowds
12/26: 9; The irony is that 12/26 is sometimes more crowded than 12/25 at some parks. This past year, AK was crazy crowded on 12/26 and 12/27. Seems like everyone goes to MK on Christmas, then over to Ak to get Pandora out of the way. Maybe the trend will shift to DHS this year...
12/27: 7; Small dip in crowds. Many people come for Christmas OR NYE. You'll see a good amount of people check out on 12/27 or 12/28 and head home for NYE
12/28: 7; See above.
12/29: 8; Runners start checking in. Suddenly you walk the resort and there's runners everywhere. NYE'ers start checking in
12/30: 9
Okay, now a bunch of thoughts with no true semblance. I'm just typing and seeing what comes to mind...
Look, it's going to be crowded no matter how you cut it. But there's absolutely ways to "beat" the crowds.
As a rule of thumb, we always go early, take a break in the afternoon, then return later. It's hard with a 5 year old, but it's doable. The parks don't get BAD until 10 or 11am. By noon, you'll "feel" the crowds. The area by Small World, Main Street, and other normally congested areas will make you feel claustrophobic. During Xmas, Disney will have morning EMH at MK from 7am-8am. DO IT. Go and get on as many rides as possible. Book FP+ selections from 9am-12pm, then leave. Go back and relax by the pool if it's warm outside.
It's worth springing for a park hopper during this week. MK too crowded? Hop over to Epcot.
Pack for all different weather. It could be 85 degrees and sunny one day, then 50 degrees and 30 at night the next.
Stay on-site. This is the trip to stay on-site. For one, Disney transportation. Second, traffic is INSANE during Christmas week. Keep in mind when you go to MK, you'll need to park, then take the ferry or monorail over there. Not fun.
Pack light. If you can go sans bag, then do it. Security takes up a lot of time when going into the parks.
My cousin brought her 4 and 2 year old during Halloween. It was the closest (crowd-wise) I've seen the parks. Just keep your kid in a stroller when it gets crowded.They wouldn't stay in the stroller long and were fine.
Use the park layouts to your advantage. This is especially important during this week. Disney will open backstage areas (behind Main Street) to alleviate the crowds. Parade going on and you need to leave MK? Walk through Casey's and the Emporium gift shop to leave. Watch the parade from Frontierland, where it starts, then walk through . the breezeway over to your FP+ at Jungle Cruise.
You'll pack a lot of different things for this trip. Remember to pack your patience. People are either in slow motion or fast forward. Many people forget to pack their manners, so just grin and bear it.
The parks are great, but the resorts are AMAZING too. Go to Grand Floridian, Contemporary, Wilderness Lodge, Beach Club, Yacht Club, Boardwalk and Swan and Dolphin. All are beautifully decorated. Disney Springs will have Santa until 12/24, then Santa Goofy. Bring your little one to meet him, then grab a free chocolate at Ghiradelli.
Do the holiday-centric stuff: Jingle Bell Jingle BAM if they bring it back, pictures in front of the castle when it's lit up with icicle lighting, Candlelight Processional, etc.
Look here's the thing... we're an older family. Does it get tiring? Absolutely. Is it crowded? YEP. Have we considered going elsewhere? Uh huh. But it's amazing. Nothing beats Disney during the holidays. It's crowded, but it's also gorgeously decorated and our favorite time of the year. You can't beat it. It's not for everyone and you'll get a few people on here that'll yell "don't go!" I can't recommend it enough. Go; take the afternoons off; get your FP+'s; use EMHs; plan your days, and you'll be fine.