Cakes are usually associated with sweetness, especially among children. Kids love sweet things and that is why they always see a birthday or any special event as the time to enjoy. For your birthday cake, you could choose chocolate cake. Children and adult would love that. You could also prepare cake that is not too sweet in case of adult guests who are not too interested in sweet things or who are diabetic. Having this combination ensures that everyone has a nice time at your birthday party.
Birthday cakes are also good in making people still hang around after most of the events of a birthday party. In most cases, after eating, singing and playing, cakes are used in keeping the environment lively instead of having an environment which is boring.