To Begin with:
Since this is 90's based, there is no outside knowledge of the mansion. It's the safe haven that it always was.
The X-Men (and friends) are gathered for a party; since there's no other way to offer thaks to the man that started it all on his birthday. Professor Xavier asks for only your presence as a gift. Drinks and snacks will be given, but feel free to bring a dish if you'd like.
Enjoy, because everyone knows that superheros rarely have days off. (But don't get too cozy, because you never know how long it will last)