Glad you had a great time!
As far as planning for your trip in Dec. I would consider mid-Dec around the 13th -18th. The dates you are planning to go it will be EXTREMELY busy because it's the week before Christmas. Value season really ends on 12-21 and then goes right into peak season, but it will be peak crowds by 16th I gurarantee because Christmas is only a week & a few days away, so be prepared (make lots of ADR's, FPs may run out on some attractions, etc).
In mid December the weather is usually awesome, if you encounter any rain it's usually because a cold front is coming through. It could be 60 that next day but then warm up into the 70s the day after. It varies, but I love that weather as it's very comfortable in the parks.
Mid December crowd-wise...This year you'll need to go way before the 16th or so, after that forget it, it will be PACKED! We learned that the hard way this past Dec. We went from the 16th-22nd, too busy for me. The first day was ok but by Friday the 17th everyone started to arrive and it just got so busy. I wouldn't go back again this time. (earlier--yes--but we'd be gone by mid-Dec).
Looking at the calendar this year if you want to avoid high crowds you'll want to go before the weekend of the 16th because Christmas is the following Monday and many families will start arriving the Friday a week and a few days before (the 15th). Just figure, 2 weekends before Christmas. Prior to that it shouldn't be too bad.