The best parties I have been to are those that do not go overboard on food, so a few options for the kids and a few for the adults. Keep it simple then nothing gets wasted. A sausage sizzle sounds great too.

Kids Franksfurts, fruit kebabs and fairy bread. Water to drink.
Adults, - scones/danish, tea and coffee.

Then bday cake/cupcakes for all!

A friend had a brunch party with raisin toast, muesli and fruit.
Good luck!