A baptism luncheon is one of those family milestones that sneaks up on you. Between the guest list and the church schedule, the timeline moves fast. The real lever here is lead-time, so you want to book the catering at least one month early to lock in your date and avoid last-minute stress.
We are looking at about $600 for a typical US gathering. That is a manageable number, but it still helps to break it down so you are not eating the whole cost in a single month.
Keep in mind that the intro window is a hard deadline, not free money. If any part of that $600 balance is still there when the 18 months are up, regular interest will kick in on what is left.