We are letting four kids have a pool party this summer, is it rude to ask everyone to bring something?

We are looking at about 30 to 40 kids from 2pm to 10pm with a bomb fire later in the day. I will be providing hot dogs, chips, drinks. Would it be rude to ask everyone to bring something specific? A few invites asking for a box of gram crackers, a few for a bag of marshmallows, etc? Any suggestions on wording such request?