We went that week last year, 12/14-12/20 and wouldn't hesitate to do it again. Crowds were much more manageable than when we normally visit (June/August), and the weather was so much better! Definitely take a jacket with you each morning. We had gorgeous weather, high 70s during the day, but waiting for Illuminations in the mid-40s with the wind coming off the lake...brrr!
If you want to see the Osborne Lights with less of a crowd, don't go right when they're turned on (6ish). But that was one time we actually liked the crowds...everyone dancing along to the music and grinning, it was great!
Just to add to the initial question we are planning on doing
MVMCP in your very knowledgable opinion would going Tuesday the 16th be a good night to go? I heard reports from last year that it was very crowded and unenjoyable.
Generally the common wisdom is that the later in the year it gets, the more crowded and less enjoyable MVMCP gets. Is there an earlier party night available during your dates?
We went last year on the night of the very last party, just because we'd never done it before, and honestly I didn't think it was worth it. We encountered some of the absolute rudest crowds I've ever seen in the parks on that night. Didn't feel like overall crowd level/wait times were any less than during regular hours, either. I guess the parade was cute but it wasn't worth the rest of it.
If you really want to see the holiday parade, holiday Wishes, or some of the special characters that aren't otherwise out, then go for it. Otherwise honestly, there's more than enough "free with admission" holiday cheer to go around in the parks during the week you'll be there!
