You want to give them a great send-off at the community center, and booking three months out gives you the best shot at locking down the room and dates you actually want. Big milestones sneak up fast, so starting now keeps you from scrambling for tables, sound gear, and catering at the last minute.
We can break this $600 event down into manageable chunks so you aren't hit with a massive bill all at once. By pacing out the room rental, food, and paper goods, you keep total control over what you spend.
That 0% window is a deadline, not free money, so make sure the balance is paid off before the 18 months are up or deferred interest will hit you hard.