The bar mitzvah lands on one specific day, but the spending starts long before it. Venues, caterers, and DJs book out a year to 18 months ahead in most markets, and the deposits often come due before the rest of the budget is even firm. Treat the date as the anchor and work backward, because once the venue is locked in, almost every other cost has a deadline attached to it.
A $25,000 celebration is real money, and most families don't have it sitting in a checking account. The good news is that you have a long runway. The catch is that runway only helps if you decide early how to spread the spend, what to charge, and what to pay down so nothing sneaks past the finish line and starts collecting interest.
The 0% intro APR is a deadline, not free money. If a balance is still on the card after 15 months, the standard variable APR kicks in on the remaining amount, and that rate can easily outpace anything you saved by waiting. Aim to have the card paid off at least a month before the intro window closes so there is no chance of an accidental carryover.