I understand that everyone has their own youth ministry convictions about what to do and not to do for Halloween. With that being said, I wanted to string together some ideas and hopefully there is something that will work for your youth ministry.
Pumpkin Bowling: I love this game. It’s really easy to set up and do. You will need 6 2liter bottles for the pins and 2-3 pumpkins (because they break) per bowling alley you want to create. It’s best to have someone helping with the pumpkins and someone also to set up the pins.
Pumpkin Puzzles: Each team is given a pumpkin. Make 3-6 slices by cutting the pumpkin into pieces, then each team then switches and then they have to re-create the pumpkin using tooth picks. The quickest to recreate the pumpkin wins.
Tell the original meaning of Halloween: You can gather some resources such as from wikipedia and other resources and tell the original story of Halloween. Every year you should find some kids that didn’t know the origins being an all saints day.
Stories of Christian Heroes Around a Bonfire: Utilizing Hebrews chapter 11 and 12. You can pick people in the church that have died and share about the faith they had and what they did for Christ or you could pick some from Jesus Freaks.
I would try and encourage you to not just skip the opportunity of utilizing the Halloween time to your advantage. Kids during this time are thinking of spiritual things naturally with all of the media covering the event. Did you know that Halloween is now #2 behind Christmas for decorations? Makes sense as people purchase costumes and decorations for their homes.
What other last minute ideas could you add to this list?

