For serving hot foods, think crock pots and ice buckets. Yes, ice buckets. They are insulated and will keep foods hot for extended periods. My mom has a collection of them that she has gotten at estate sales and yard sales that are great for parties. Almost everyone you know has a crockpot or two, most people will let you borrow one for a party.
My favorite halloween item was a spider cake. I baked the body in a bowl and the head in a smaller one. Then I cut a slice off of each and filled them with red jello that I had fluffed up a bit. I used twinkies for the legs and frosted it all with black frosting. It was huge but a big hit. It was a party with a lot of kids and boy did they love the oozing jello that came out when I cut into the head and the body. One of the Moms was apparently not expecting that and got sick. Surprised all of us. The kids were entertained by that too.
I have also done a kitty litter cake for kids. They loved it. I baked a cake in a 9x13 pan and left it in the pan. I put a layer of white frosting down and put tootsie rolls (without wrappers) on the frosting. Before the frosting set, I poured grape nerds all over so it was a thick layer with no frosting showing, and pressed them down so they were into the frosting. Then I poured more grape nerds on so the tootsie rolls were mostly covered. Just to make things fun, I had a new kitty litter scoop that I sent with the cake (it was for hubby's office party for halloween) for serving. Once hubby cut the first piece and people saw that it was cake, they loved it. It looked VERY realistic. I did it because someone told hubby that no one could make a cake that looked like a litter box. Oh, yes I can!