Hi MacMama0930!
Former So Cal resident and AP here...just moved to a tiny town in the midwest in August, after having lived in OC and being DL APs since 2001. Boy, do I miss it! We were able to spend 4 days at DL over the winter holidays, though.
I will tell you as a So Cal kid who spent more days and nights than she can count at DL (and later DCA) over the course of 30+ years...the sheer size of WDW is going to blow you away. You truly can't imagine it until you've seen it in person. You know how when you're at DL there is the berm once you're inside, where you can't see anything outside the parks? imagine that berm surrounding four parks and 25+ hotels. It's truly mind-blowing...and you won't believe how huge the castle is compared to the one in DL! Once you're at the "World", you feel totally removed from the outside world...and that's why, as much as I love DL, for me WDW wins hands down. I mention the size issue because I think it impacts which resort you may want to choose.
My H (also a So Cal boy) and I made our first trip to WDW for our honeymoon in January of 1994. We stayed at what was known as "Dixie Landings" back then (now Port Orleans-Riverside). It was the week after New Year's, and the parks were completely dead...as in, we walked right onto the most popular rides and rode over and over again. It was crazy! We loved it, and it began a series of almost-yearly trips to WDW, which continued after our D was born in 2002. Our hotel preferences changed greatly once we had a child, and as over the years WDW began to become more and more crowded, even in the "low seasons". All that to say...
You mentioned that you have two children, ages 7 and 10, and that they have "low stamina". If the budget will allow it, I would suggest that you strongly consider staying at either one of the Monorail resorts (GF, Poly, or CR) or one of the Epcot resorts (BC, YC, BWI/BWV) because there is so.much.walking at WDW compared to DL! Especially if you're talking about going at Christmastime...the T&TC parking lot and process is IMHO a nightmare that I try to avoid at all costs, and unless you're staying on the Monorail route or are within walking distance (or you take the bus system), you will have to endure it, lol.
About the bus system...many on this board use it and love it. As for my family, H works long hours and travels a ton on business, and my D is very busy with school and extracurriculars, so vacations are a rare time when we can all be together for an extended period of time. Because of that, we don't like being beholden to the bus system's schedule or the fickle finger of fate as to whether we can just make it on the first bus or have to stand around for another 10+ minutes waiting for one...and that's doubly true for us when we're exhausted after a long day at the park...or if you get sick (which has happened to everyone in my family at least once). We used the bus system when we were younger and before D was born and typically were fine with it...but has life has gotten more stressful for us and time matters more than money now, we avoid it. I guess that makes us impatient, lol...but it is what it is. In the past we have rented a car and driven to AK (again to avoid the buses), but I think this year we will try out the new Minnie vans instead.
So what I would advise is to try to figure out which park(s) you plan on spending the most time at. If it's MK and Epcot, I would recommend staying at the Poly, because IMHO it has the easiest transportation to both of those parks...you can catch a direct Monorail to MK from the hotel, or you can take a short walk to the T&TC and take a direct Monorail to Epcot. If the budget would allow, staying in one of the 1 bedroom villas there would be ideal, because it would give everyone a little more space and privacy (the older my D gets, the more that matters to us). Alternatively, you could stay at Bay Lake Tower at the CR...you can actually walk or take the Monorail to the MK from the CR, but you'd have to switch Monorails at the T&TC to get to Epcot. When our D was younger, we stayed at either the Poly or the CR to take advantage of the easy transportation to and from MK, as it was her favorite park at the time and where we spent most of our time.
If, however, you think you might spend more of your time at Epcot and HS, I would recommend one of the Epcot resorts. It's a quick walk or boat ride to either Epcot or HS, the pools are amazing, and the Boardwalk area has a lot of great food options. Now that our daughter is a teenager and prefers Epcot and HS, our favorite place to stay is at either a BW or BC 1 bedroom villa (again, for privacy...and I love that they have a washer and dryer in the suite because it means we can pack less clothes). Plus, we think the food at Epcot is the best in all of WDW, and it's awesome to be able to eat at Epcot every night if we feel like it and only have a short walk back to our hotel. (As a side note, you won't believe how much better the food is at WDW than it is at DL!!!)
AKL is amazing (we've stayed there twice), but at the time of the year you're talking about going, I think I would avoid it. It is the farthest away resort from any of the hotels (it's not even that close to the AK, lol), and you would have to get on a bus or in a car every time you wanted to go anywhere...and with crowds at that time of the year, again, I think that since your kids are used to the size and scale of DL this could end up being an issue. I think if you were willing to use the Minnie van service or Uber to go to the parks (and avoid the buses) you could maybe still consider AK...but again, you'll be waiting on that Minnie van/Uber at one of the busiest times of the year at WDW.
MVMCP will blow you away...we have nothing like it at DL. And the Halloween parties at DL also can't compare to the ones at WDW...everything is just on a grander scale. And the Candlelight Processional at Epcot...again, incredible...if you can talk your family into it (and if your kids can tolerate it), I would do it.
We just went to the WOC dessert party in December, and it was awesome and inspired us to book some dessert parties for our trip to WDW in April (fingers crossed that they are just as good or better). I'm sure others will chime in on ones you might want to consider.
The CL thing is highly subjective. We've done it once at the GF, and we found that with the dining plan, it was too much food for us, and we'd rather save the stomach space for Epcot food, lol. But there are tons of people on this board (I've been lurking for many years and only recently started posting) who swear by CL and always stay that way.
And the last piece of advice I will leave you with is...if you have any desire at all to not eat counter service for every meal, take the 180 day ADR thing seriously!!! There is so much more planning that goes into a WDW vacation than a DL one (though reservations have been harder and harder to get at DL restaurants too). And get those fastpasses as soon as you can too...you won't believe how many more people who go to WDW plan and reserve everything in advance!
I hope this has been helpful...sorry it's so long! I was excited to "meet" a fellow DL vet...and so excited for you to be able to take your first WDW trip and (hopefully) fall in love with it!