A private tasting is all about the atmosphere and the conversation. You want a weeknight slot to keep the cost closer to $450 and ensure the venue can focus on your group without the weekend rush.
Booking at least six weeks out is your best move for availability. Once you have the date, you can manage the payment in a way that keeps your monthly cash flow steady.
That 0% window is a deadline, not a gift. If you still have a balance once the 18 months are up, the bank will start charging interest on whatever is left over.