Hi Macsilk, I love wiggal's idea! Themed food is always great. You could go for chinese or indian (easy on the spices though for kids that might be fussy, or provide an alternative). The supermarkets have those party food packs, Morrison's do mixed Chinese starters, mixed Indian starters etc. for a good price, or you can go fresh at Deli counters. You could go Italian, and get those mini pizzas, garlic bread, tiny pasta portions or cold pasta, and a big bowl of mixed salad.
Or you could set it as a tea party, with little fairy buns and sweet cakes, and various sandwiches and buns all arranged nicely.
Have a great time whatever you decide!