That moment when the smoke clears or the box opens is the whole point. You want to be present, not stressed about the receipt, so let's break down the spending into a timeline that actually works for your bank account.
A backyard party is great because you control the variables. If you treat this like a project with a clear end date, you can keep the costs around $900 without feeling the pinch all at once.
The 18-month intro window is a deadline, not a free pass. If you still have a balance after the 18 months are up, the bank will start charging interest on whatever is left, which will cost you more than you planned.