I'm about your daughters age and have catered for large numbers before. Surprised by the number of suggestions to make mini stuff - what a faff and a bit 90s!
Firstly I'd base the menu on veg, and have one meat option rather than the other way around. Yottelengi style eating is the way to go.
Shop bought:
Falafel, buy big bag of frozen from an ethnic supermarket so much cheaper and tastier than Tesco's. Crisp up ahead of time.
Selection of dips, served in bowls and topped with herbs or something to look good. Plain good hummus (weird flavors are not good...), babaganosh, maybe whizz up a yogurt based one fresh. Also put out nice olive oil and balsamic.
Selection of other shop bought antipasti, stick with simple like olives rather than any weirdly flavoured seasonal specials.
Mix of fancy hams, cold cuts etc for the carnivores.
Make at home:
Several trays of loaded focaccia. Can be served hot or cold, cut into squares, and you can always "cheat" with the supermarket bake at home mixes. Maybe offer two toppings, one vegan like med veg, one veggie like butternut squash and feta.
Couple of bowls of chopped salad (Not leaves!!). Maybe chopped caprese (let people dress it themselves) and a rainbow slaw.
The only thing you actually have to cook in the focaccia and it's dead easy because you just do it in slabs.