The only museum that is open on December 25th is Palazzo Strozzi where you will find the Jeff Koons exhibition at the moment. I believe Palazzo Vecchio might also be open, but I'm currently checking all the museums out to see their hours for the holidays and don't have a full idea of whether Palazzo Vecchio has confirmed for this year. I'll post an update as soon as I'm done, if you can wait another day or two to finalize plans. If you're eating out, make sure to call and book your restaurant to ensure you have the table.
That’s a good sign then!! I haven’t seen any official post or notice and last year it was closed on December 25 but if ticket sale is open for that day, then it means they plan on being open that day. Thanks for letting us know!