I think you can do one half day at a park, but that week is very, very crowded. Just expect a lot of people at the park that afternoon. You may not get to ride a lot of "big" rides. Just expect to enjoy the parades
This.... We recently cruised and I thought about doing a 1/2 day at the park a day before our cruise. BUT our train arrived in Orlando at about 11am. We got the rental car and drove to our port hotel. Now, we didn't have to get up early that morning as we slept overnight on the train. We were allowed to check-in early but honestly we were still so tired that we just walked around, ate dinner and got to bed early. We felt very relaxed the next morning and getting up early for the cruise wasn't a pain and we enjoyed a leisurely breakfast at the port. You will be getting up at least somewhat early to be in the airport for your flight if you are arriving at 11am. Here's another thought- Are you planning on buying your DW tickets ahead of time? What if your flight is re-scheduled? If you decide to go to DW, then I would personally wait to get tickets then. BUT, I have heard of DW closing its gates around Christmas-time because it was so packed, even by 11am, that they HAD TO. If this is your first time, then I wouldn't personally go to DW that close to Christmas UNLESS opening hours are until really late AND you can wait to get tix that day. I wouldn't tell the kids if possible though. That way- if you can't go for whatever reason (plane delay, park is closed to no more entries, etc. etc.) they won't be disappointed. Their age though is a really big factor. I wouldn't bring a 3, 4, 5 year old to the park and plan on staying that late after a day of travelling to get there.
Plus, most fast passes will be gone by the time you get there!!
OR, another option is....Ask how late your hotel check-in can be. You might want to get off plane, get rental car and head straight to DW! Then, maybe check in late. Some places have 24 hour check in.
I have been *near* Christmas-time and I remember us saying over and over that the LATEST we'd want to be headed to the parks is Dec. 18th OR if any date later then we'd be first in the parks. I just don't want it ruined for you if it is your very first time and you arrive 1) Exhausted from travelling 2) So many people and all fast-passes gone, etc so you can't even enjoy yourself.
As for the Very Merry Christmas party- Now we have done that. We enjoyed ourselves, BUT out of the whole week we were there (something like Dec. 11-18th) we waited the longest in lines that night because they close the fast pass machines. However, the atmosphere is especially festive with all the elves constantly handing out cookies and chocolate milk...and I do so love the parks at night all lit up!

But decide NOW because the Christmas parties sell out fast! (Oh and another thing to note- not every ride/attraction is open on the Christmas party nights!)
Yet another option is checking in EARLY to your hotel. Some hotels charge an extra fee for that, but I've been to ones that don't. (As previously mentioned, the Radisson at the Port check-in wasn't until 3 or 4 and we checked in at about 11:30 or 12.) So that might get you into the park a little earlier too if you'd rather check-in before the park.
So if you could answer (sorry if I missed it in other posts):
1) General ages of children? Are we talking toddlers? Teens?
2) Is this your very first time going to one of Disney's parks?
I think that might help us further give you better advice.
