The big thing for Halloween now is 'scary food', which can just be ordinary food with special decorations. For example, you can make a large or a lot of small cake and decorate them with spiders, skulls etc. There is a good selection of these kind of recipes here. This selection also includes seasonal but less gruesome recipes, like the pumpkin face cookies or the mini toad in the holes.
If you're getting away from the 'party food' idea and looking for a meal, anything with pumpkins is a good idea - soup or pie, for example - and apples have a Halloween connection as well because of all the games like apple bobbing. So apple pies and cakes will go down well too - and toffee apples best of all.
To make it easy, why not do one big 'scary' cake, with black icing etc and some fun things like toffee apples, have a big pot of pumpkin soup and then something easy and seasonal like 'eyeball pasta' or baked potatoes with lots of different fillings.
Have a great party!