225 guests is a daunting number to self cater, in my humble opinion. Hope you have lots of help 'cause you are going to need it and will be a kitchen slave.
Some ideas to consider... and I'm no teenager.
Buffalo Chicken Meatballs - in a Spicy Sauce with Blue Cheese or Buffalo Chicken Dip.
Devilled Eggs with Bacon & Cheddar (buy pre-boiled eggs)
Caesar Salad anything.
Sliders (mini burgers) would go over well.
Or consider a Gourmet Hot (Haute) Dog Station with fun toppings
Pasta Station (Cheese Tortellini is good in case there are vegetarians). Use Chinese Take Out Boxes to serve!
Check with your Children!
S'mores for dessert!