what a lovely daughter you are to go to so much trouble to planning this special event, if i were you i would ask everyone to bring a plate of food, that is what we do in NZ, when money is tight, as they are family members no-one should mind, have a list of things, and tell each member what you would like them to bring so you don't double up on things,but finger food is the way to go i think if you want to keep to the budget.

I agree with the others, concentrate on getting a really yummy cake, that not only looks great but tastes divine.