(We made a lucky dip barrel for this at our youth group)
Ask the kids to each come up with a prayer topic (eg. Youth group, government, Africa, non Christian friends, war, etc.) Write the topics on pieces of paper and put them in the barrel (or on the wheel). Choose someone to come and spin the barrel and then pick out a topic. Repeat the process till you have 3 or 4 prayer topics and then ask the group for prayer points under those topics. When there is enough prayer points, pray through them as a whole group out loud.
40+ Note: If there’s more than 40 people, you can either: 1) limit the to just 2 topics; 2) select just a few of people (maybe 1 for each category) to pray the prayer points on the board; or 3) split into small groups to pray.