Summer weekends fill up fast, so booking your lawn games at least three months out is the only way to get your first choice. You want the giant Jenga and cornhole sets available when the weather actually turns, not whatever is left over.
A rental package usually runs around $350. By breaking that cost into smaller chunks, you can clear the bill before the season is even over without feeling a pinch in your monthly budget.
Remember that the 0% intro period is a deadline, not free money. If you have a remaining balance after the 18 months are up, the bank will start charging interest on whatever is left, which gets expensive fast.