You could have go for foods all from one country, such as do an Italian meal, Mexican, Indian, Asian, French, anywhere really.
Italian - you could have antipasti (Italian meats, breads, olives, artichoke hearts, roasted peppers, etc - a lot of these can be bought pre prepared and just put together in bowls and plates) followed by a risotto or pasta course, then the meat course (perhaps saltimbocca but using thin turkey or pork steaks instead of veal) with salad and selection of veg served separately in big bowls and finish with a dessert (could be something simple such as ice cream, which you could do yourself in advance, or tiramisu, which I've made the day before and has been fine).
Mexican, Indian and Asian - for these you can do lots of different dishes for people to tuck into as they like so keeps everyone happy!
Mexican you could have quasadillas, nachos, enchiladas, chilli, etc followed by some exotic fresh fruits cut up and served on a platter.
Indian - lots of different dishes you could do for this.
Asian - go fo things from different countries, such as Malaysia, Japan, China, Thailand so that people get different flavours.
Hope you have a great birthday!
Helen