This is a great way to test everyone's creativity. For children, it is best to not impose a theme. Many children know what they want to be for Halloween months before and will be crushed if they can't come as a witch or their favorite Superhero. When preparing food for a Halloween party, don't forget that nearly any food can become festive with a little food color. Cookies and cakes can be turned blood red, or Halloween orange with just a few drops.
Children love to get candy, even though parents often end up throwing half of it away.
Turn food into an activity by having unfrosted cupcakes for each child. Set up a decorating table and let each child decorate their own cupcake. You can have plastic spiders and other small Halloween items for the children to use. For adults, set up a table with lots of Halloween decorations and several types of finger food. A tray with carrots and black olives fits the color scheme.