Christmas Day & any day, yes.
If you want to have a meal here on Christmas, I woud call in a reservation.
The restaurant does have multiple restaurants within. Aside from that there are numerous restaurants in and around the vicinity of the hotel that should accommodate your needs.
You can call the hotel to confirm but they have offered events to the public in the past in both their event space(ballroom) and restaurant (Lorenzo's) for a fee. Sometimes it is regular menu, pre fixe, or buffet. There should be some food service available one way or another.
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