Meals I’ve successfully eaten with ‘fussy’ eaters include:
Mexican - put out wraps, rice, grated cheese, selection of dips/spreads (hummus, sour cream, guacamole, salsa, mayo, tomato ketchup, BBQ sauce), lettuce, cucumber, peppers, sweetcorn and then serve A) breaded chicken strips/nuggets B) plain chicken breast C) chicken cooked in spices.
Italian - garlic bread & plain baguette, salad (served as separate items, not mixed), plain pasta of 2 types e.g. penne and spaghetti with A) smooth tomato sauce B) bolognaise sauce, platter of sliced meat and then cheese to grate. Add pizza (plain margarita) if need more!
Buffet with chips! - lots of options for plain stuff not mixed (see salad as above) and then add e.g. sausages, quiche/pie, plain roast chicken and serve with a lot of chips!