Autumn parties are better with hot chocolate and fresh churros. Booking a mobile cart usually requires a deposit several weeks out, especially if you want a specific date. To save money, look at weekday evenings when caterers often lower their hourly minimums compared to busy Saturdays.
Planning early gives you time to handle the logistics without a massive upfront hit to your bank account. If you use the Citi Simplicity® Credit Card (Citi), you can pay for the catering over a year and a half while avoiding interest charges.
This isn't free money, it's just a way to delay the bill. If you still have a balance after the 18 months are up, the interest rate will jump significantly, so make sure you pay it off on schedule.