Make a batch of playdoh,
like this: www.instructables.com/id/Easy-Affordable-Play-Dough/,
or maybe even an edible kind like this: https://www.instructables.com/id/Cookie-Doh-Play-Doh/
Roll it thin and cut your ghost form with a butter knife. I made my ghosts about 3-4cm high.
Dry in the oven and then wait a few days.
Drill a 2mm hole. I used a regular drill and my trusty hands.
Paint black eyes and a mouth with water paint.
Measure 60cm string, tie and attach to the hole.
Hand it out to the kids along with the candy. It's up to you if you tell them if it's edible or not...;)