Do you have any Indian sweet centres near you? They will often do catering of Indian food.
Even if they don't cater my local sells samosas for 25p each and other Indian snacks.
If you decide to do it yourself hire a catering fridge, get some of those trays with compartments that look like you would get in prison.
You can make up the trays with cold food the day before and refrigerate, if you have 6 compartments I'd do
Salad - no dressing
1-2 samosas
Some sort of savory snack, sausage roll or scotch egg or mini pork pie.
A bread roll and a butter (catering pack of those mini butters) Add a napkin and plastic cutlery.
Mark the vegi / vegan ones separately
Put a selection of condiments on a table.
On the day hand out the trays and have 2-3 hot things, a BBQ, selection, rice or potatoes (mini baked potatoes are quick in an air fryer) or both. Veg chilli and maybe something else, pizza or quiche or rotisserie chicken from the supermarket.
Have someone serving the hot food, teenagers are good at that.
Get paper plates for cake / pudding.