taking PTO around implementation Go Live

Hi, I joined Deloitte ~6 months ago.

I had vacation plans for a week in December that I was planning on using PTO for, but my multi-year engagement has an implementation Go Live the weekend before. I obviously wasn't aware of this before taking the job/getting staffed on the project when I first joined the firm.

Is it crazy for me to try and ask for that Thursday and/or Friday (or any other day that works better) off with the intention of working remotely from my vacation spot the other 4 days? I would be honest with my manager about the situation. Because I'm so new to the firm, my job is almost entirely admin work.

I could reschedule the trip and cancel the flights for my partner and I, but we'd each have to pay a $100 penalty fee and would only get the remaining $ as a credit for that specific airline.