There's a fun cover on the Ocotober issue of Country Living; that cake would make a great centerpiece with its spider webbing--and spiders--all over the cake! The webbing is made from gooey, melted marshmallows; the spiders are made with black fondant, though possibly black licorice or Twizzlers might work as well. For a fall decorating idea, you can decoupage pressed leaves on white gourds. Check out this issue for more home and Halloween decorating ideas.
Collectibles include old school microscopes, which I think kids could have fun with too.