M.S.
Yikes! That's a tough one. I get it- wanting to cut down on all the junk, but it makes it harder for the parents!
How about fruit/veggies- but arrange them into a scary face once you get there? A couple plates with grape eyes and carrot teeth into a scary face? Or a pumpkin shaped out of carrots? The kids might like grabbing the body parts. You could provide ranch dressing or hummus to dip them in?.