Hi!
The weather in December is pretty tough to predict! Since our family
loves to travel to the parks in December l, we've
had quite a few trips in that time frame. Most of our trips have had
great weather with mid 70's during the day. These temps combined with
the Florida sun can make for fun pool days. Occasionally however, we've
also had trips that have been pretty cold, even during the
daytime.
My best advice for December trips is to be sure to pack your bathing
suit and hope for some famously great Florida weather! AND, of course,
it never hurts to bring Pudge the Fish a sandwich or two (Hey, it worked
for Lilo!)!
One must have during your trip will be a double stroller. Its up to you if you'd like to bring one with you (handy at the airport if you're flying) or rent one at the parks but either way its a must have! There is so much walking during a Disney trip even kids who don't typically ride in strollers will want one.
As far as toys go, we've always been light packers. We tend to only pack what we'll need to keep the kids busy on our travel days (airport, car, train - however you may be getting to Walt Disney World). Once you arrive at the parks, there is so much to see and do that we've never needed the distraction of toys. Plus, its hard to resist picking up a few new, unique toys once you get there!
My fellow Mom Joanne and Dad Angelo have some great tips and ideas for touring with little ones. Check out
this answer and
this one too! And last but not least,
this answer too!
Have a great trip!