Defintely do the Fantasmic! buffet!! We were there last year the 26th-30th and it was PACKED!! The closed the park on the 27th, 28th & I don't remember about the 29th. We actually went to Knott's on the 27th because the park was just absolute ridiculous! which was nice, can't be Mrs. Knott's chicken dinner
If you have an ap(that's not blocked)or a park hopper, I think is what they were saying, you can get back in if you've left and they've closed the parks. I'm 99% sure that's what they told us.
Get there EARLY, the lines for the bag checks can stretchhhh out into DTD, and head straight to Fantasyland(like you just said, duh LOL)
If you are intereseted in Napa Rose, Goofy's or Blue Bayou, make your ressies as soon as the dates allow. So you can get a spot.
If you do Blue Bayou for lunch, that way you can get a monte crisco!, then make it for 11:20/11:30 and you'll be one of the first seated(still request a water table though)you can go do all of fantasyland, small world holiday and then make your it to Blue Bayou, while you are waiting to be seated have someone in your party go fastpass Haunted Mansion Holiday. That way as soon as you are done with your meal you can head over there and ride it.
I know the WDW Florists have small christmas trees for WDW, I would call the GCH and see what their planner's there can come up with. I know you can get really cute things like milk & cookies delievered to your room, tuxedo strawberries etc etc etc. Maybe, they have some sort of Christmas thing also.
Another idea would to bring your own disney stockings and fill them up! How cute would that be!
HTH
Tina