While many of your participants may not keep Kosher, Kosher on a Budget offers a great breakdown of how to prep a Holiday menu without breaking the bank.
Rosh Hashana & Sukkot Prep on a Budget
Planning for Rosh Hashana: Getting Organized
Inviting Guests, Making a Budget & Meal Planning for Rosh Hashana and Sukkot
Shopping Lists for the Jewish Holidays
Rosh Hashana Post-Mortem with Recipes
Apple Challah Recipe for Rosh Hashana
Peach Noodle Kugel Recipe for Break-the-Fast
Pesach Prep on a Budget
How to Shop for Passover on a Budget, Part 1 and Part 2
On Passover Bondage & Credit Card Debt
Frugal Hostess Gifts for Passover Seder
Passover Menu Planning Made Easy
Challah image by Grongar, licensed under Creative Commons.