We went over Christmas - NY in 2019, 2020, 2021. We are missing 2022 due to work schedules, but it's been a wonderful time of year to visit - despite the relatively high crowds each year.
2019: RotR had just opened, virtual BG only, pre-pandemic. Crowds unlike any I'd seen before or since.
2020: everything at reduced capacity, no FP or
Genie+ (except RotR still virtual BG only). Not crowded at all, but still had lines for some things because of reduced capacity. 12/30 was a really busy day - due to spacing the Test Track line at open stretched almost back to the Christmas tree!
2021: pretty darn crowded even though we were in the first omicron surge here - but Genie+ helped a lot.
I think if you go with measured expectations, you can/will have a great time. It is very festive and there is a lot to do, see and eat and it's not only about the rides. We were still in stroller age in 2019, and used a stroller in 2020, 2021 as a crutch/sitting spot when the kids got tired.
Expect there will be crowds. PP were right, a lot of people won't rope drop, especially on Christmas and New Year's mornings. If you're aiming for rides, use early entry (and rope drop *that*) - we got the most done in the 1-2 hours that the park was first open. Back in 2019 we managed an inordinate # of rides in the early morning and had some great pictures of a nearly empty MK.
Have a plan for eating. If you're doing QS, mobile order is your friend, but aim to book your meals well before you plan to eat, as some places will fill up very quickly. Or eat at off times, but that can be hard with little kids. We generally booked a sit down meal for an early dinner, and tried to have snacks on hand in case ride queues went long or mobile order was a mess.
In 2021, Genie+ really helped. I did get up before 7am to book the first ride and buy our ILLs, but then by the afternoon was able to stack a number of rides with a minimum of waiting. Alternatively, if you don't want to do the 7am dance (and really who can go back to sleep after that drama??) you can sleep in and still book things in the afternoon. Just don't assume you'll get all the headliners you want when you want them.
Stay positive: We had a few issues with Genie+ while we were there, and approaching with a smile and a request got us the help we needed. Note: they did enforce G+ times much more than the BG/ILLs that you pay additionally for. If you're 15+ min late for your window, you may be out of luck. So if you think you are running late, you are better off modifying and rebooking. Or be prepared to ask nicely but get dinged anyway. One time we were 20 min late to FEA after running from dinner in Japan - service was super-slow due to staff shortages and our meal had taken over 3 hours. We may have brought our receipt, but ultimately didn't have to show it....
Despite the crowds, there is still plenty of room and time to stop and enjoy the unscheduled - parades/cavalcades, dance parties, resort decorations, shows ...
How old are your kids? Mine ranged from 3 - 10 in the years we've visited over the holidays. They loved the gingerbread houses at the resorts, and while they loved the headliner rides, they also enjoyed riding the tea cups and carousel, and the people mover. My two top tips would be: use
early entry + rope drop if you can, and
plan ahead for meals, whether it is an ADR or QS/mobile order.
