Therese,
There is no doubt that the
Mickey's Very Merry Christmas Party, as well as the
Mickey's Not So Scary Halloween Party, are really fun events that I typically find worth the extra money. They give you lighter crowds to contend with to get on rides, and the themeing and spirit in the park is pretty intoxicating!
That extra time comes in
extra handy if you are there in late December when the parks are so much more crowded than during the regular times of the year. Those extra hours may mean getting on attractions that you would have otherwise missed.
I will say, however, that as a Dad of a 1 and 3 year old with pretty early bedtimes, I have a hard time making that kind of investment when I can't really take full advantage of all the extra time the parties offer.
So my bottom line, for you, is this;
The party
IS worth the extra money, but only if you know you are going to be able to keep your 3 year old up long enough to take advantage of these later hours. Otherwise I would save it for a future visit!
Have a magical vacation!