Since Halloween and Fall parties are right around the corner, I'd like to share with you a few ideas showing what I've done in the past.
Here are treat bags and cookies I made for my son's class last year. I made pumpkin sugar cookies and assembled treat bags. The treat bags have a fun sucker and Halloween packaged-popcorn that I purchased from Sam's Club and a small coloring sheet with a melted crayon pumpkin (see last bottom picture for a closer look at the crayons).
For the melted crayon pumpkins, I used a Wilton silicone mini cupcake pumpkin mold; had my children help me remove the wrappers from broken and very used crayons; snapped the crayons into smaller pieces if possible and placed in the molds. We baked the crayons at 350 degrees for about 10 minutes. You can check them before that. As long as they're all melted, they're ready. Let them cool for a while before popping them out of the molds.
For the coloring sheet, I drew a pumpkin on InDesign, made 6 per page and printed off enough to have for all the children in the classroom.
I put the crayon and color sheet in a separate bag with a tag so the kids would know it's not candy.
It was great to see them get the pumpkin out and start coloring right away. When you melt different color crayons together, you never know what color will go on the paper -- I think that's the fun part for them!