Make a centerpiece with a large soup pot filled with different types of cooking utensils. Make cheese wedges from construction paper and hang them around the party area. Use yellow, blue, green and orange for streamers and balloons. Buy a Ratatouille poster and hang it in the party area.
Put out a tray filled with different varieties of cheese. It's probably best to keep it to types the children have seen before Swiss, cheddar, American and provolone are all safe bets. Serve a batch of Ratatouille. You can make it ahead of time, or use the making of it as an activity at the party. Children are more likely to eat food they've helped prepare, so having them help decrease the likelihood of you being stuck with lots of leftovers. Serve sparkling cider in plastic champagne glasses, and tell the children it's French champagne. Make a birthday cake that looks like a wheel of cheese. Bake a round cake, and frost it yellow. Use black icing to draw black holes here and there on the cake.