My DD is now 11, and has been to WDW every year since she was 2, and twice when she was 3. The toddler years were some of my favorite trips. Those years we went in December right around the time you are going, or the week after Thanksgiving. She was a high energy night owl. We would go for 8 nights. She wanted to do parks all day every day- no off days for us. She was also a rope drop (well we usually did 10 to 20 minutes after rope drop to avoid the lines- as she was not a get there well before rope drop kid) to almost closing; nap in the stroller during the day, kind of kid. Once she was awake (and that was the hard part since she is not a morning person), she would be standing at the door dressed and ready with her stroller telling us to hurry up. We always ate breakfast in the room- she was a very picky eater, so at those ages, we typically had garden grocer delivered so we would have something we knew she would like.
We would schedule a TS for lunch which was a good time for us to rest and recharge and it would also wind her down so that she would nap in the stroller after lunch. (Also, DD gave up naps entirely on her 3rd birthday- except for at WDW-she would still nap in the stroller once or twice every afternoon at WDW) We tried going back to the room for a nap break once (the first day of her first trip) when she was 2, and it was a disaster. Some kids are room nap kids- ours was not. Ours was an angry to have been taken out of the park kid who stood behind the curtain and refused to nap for 2-3 hours until we finally gave up and went back to the parks. She threw a whopper of a tantrum when we pulled our out of the park to go back to the room too. It was a total waste of time. That was the only tantrum I remember from her 2 year old trip- she was much better behaved at WDW than at home. (She had a whopper tantrum at 3 about having to leave WDW to fly home- but that is another story). The going back to the room rest period did not fit her personality at all. Also, DD never rode in a stroller from the time she was 12 months old and took her first steps EXCEPT for at Disney. At Disney, the minute she realized how big it was, she had no problem with the stroller. We did the stroller through her 5 year old trip. The 6 year old trip without the stroller was probably our roughest trip. She did not quite have the stamina for all that walking yet, and we also missed the convenience of storing stuff in the stroller as we walked around. Another year later, and she was back to open to close and walking the whole way. I would say absolutely plan on a stroller for the 4 year old as well as the 2 year old.
Every kid is different. My niece is nothing like DD. She has never been a high energy child-- I would say she was more a low energy type. She was a nap in the room in the middle of the day and still leave well before closing kind of kid.
I think if your kids have not been yet, it really is kind of trial and error and hopefully the same thing works for both. I would say just stay kind of flexible and see what works for you.