You are picturing the room full of family, the food, and the tiny clothes already waiting on chairs. A baby shower brunch two months before the due date gives you a solid runway to pull it together without last-minute scrambling.
A typical US event runs about $800, which means lead-time is your real lever here. You want to lock down the venue and the head count early so the rest of the timeline falls into place.
That 0% window is a deadline, not free money, so make sure the $800 balance is paid off before the 15 months are up or standard interest will kick in on what is left.