How to get a person to trick or treat with you and your friends?

There's this guy at our school. He's cool, and my sister would really like to go trick it treating with him. So far, the plan is me, my sis, 3 friends. I'd like to get him to go with us, but he thinks that we're too old to trick or treat. What could we do to get him to go? He's really relaxed/mellow, he likes all of us, and he's pretty nice. He isn't a very good student academically, but he's good at sports. Any ideas?? Thanks in advance!