I've got a bit of experience with these questions. We've been there every TG for the past 3 years, and this year we'll be just down the street at the Grand Floridian.
Crowds... TG week builds toward Thursday-Saturday crowds that are very large. However, you'll have the weather on your side (beautiful temps), but if you plan your attack a little, the use Fastpass, you'll have a great time. BB is quiet, if you can handle a water park in cooler temps.
Christmas Decorations: Absolutely. The bad news this year is the Osbourne Family lights at MGM will not be up this year.
Restaurant: There's turkey everywhere. Pick your favorite and it's sure to be memorable. This year, we're going to try for LTT.