You SHOULD be able to book fast passes in the 4-7 window. However, there are many reports that all fast passes that ran past the 5:30-6:30 on nights this year that have a
MNSSHP were cancelled. Some got their FP's back by calling and getting them replaced with "anytime" FP. So, yes you can, but to be safe I wouldn't book anything that went past 6:25. I don't know they'll do the same with the Christmas party, but I would not be surprised.