You want the day to feel like a celebration, not a math problem. The real lever on a graduation open house isn't what you spend — it's when you book things. Catering equipment, rentals, and big orders fill up fast once April hits, so the prep that happens in January and February is what makes the May bill feel manageable.
The good news: a milestone like this is a planning purchase, not a panic purchase. Spread the cost across the months you have, lock in the vendors early, and the open house can look generous on the day without stinging for a year after.
The 15-month intro APR is a deadline, not a discount. If there's still a balance on the Discover it Cash Back card when month 16 rolls around, the standard APR kicks in on whatever's left, and that part starts costing real money. Clear it by the end of the window or pay well ahead of schedule.