The best food is stuff you can make the day before so you just have to plate it and/or heat it up. Spanikopita (spinach and feta filos) always works well, same with all the other party foods like mini pies and sausage rolls. Keep it simple - don't try to be too fancy. Most teens like to eat the standard party food. Oh and don't forget the chips/nibbles on the side - and dessert!