Hmmm... have you ever tried pumpkin butter? It's delicious and veg*n. omnis love it too, it's really sweet and yummy.
maybe a crazy boa or tiara for the hostess, or you could carve/paint a pumpkin for the party or fall-scented (i.e. pumpkins, leaves, woodsy, etc.) insence or candles or potpouri. a basket of squash/gords.
a string of tacky jack-o-lantern lights?
Good Luck! keep us posted on ideas you may be mulling over!