K.S.
Hi, that sounds so fun! We did some Halloween games for a class party when my daughter was 6, so a couple of things we did:
mummy wrap- we divided the kids into teams. one person on each team is the mummy and the others have to wrap them in toilet paper to 'mummify' them. Whoever finishes first wins.
the other one was that we took a long sheet of butcher paper (enough to allow 3-5 kids to stand next to each other behind it and only see their feet). We drew ghosts, witches, etc. on one side. The kids stand behind it and the others have to guess who is who based only on their feet. This one was kind of a pain, but was actually the kids favorite. You could certainly change it and use something easier than butcher paper (like old sheets or something).
The last thing was a relay race. Blow up balloons and decorate like halloween items- pumpkins, ghosts, etc. The kids had to race back and forth carrying the balloons on a spoon. This was really fun, too. And easy!
Have fun and good luck!