I realize I'm a little late to the party here, but I would suggest the book "A Taste for Rabbit" by Linda Zuckerman. The themes in it will appeal to teens and adults and the conditions the foxes are living in at the start of the novel somewhat echo Great Depression or the Cold War depending on you view it, which might be an interesting conversation starter between the teens and seniors who lived through those time periods.
I think this is a fantastic idea! There do not seem to be enough opportunities to bring together youth and elders. Sharing ideas about books would probably be surprising to both age groups.
I would like to offer ten free copies of my YA historical fantasy, Night of Pan, first book of the Oracle of Delphi Trilogy if you'd like to use it for your group. There are even suggested questions for book clubs on my website as well as the answers to the Study Guide Questions that are in the back of the book. Night of Pan received five-star reviews from the Literary Classics Review, Peter S. Beagle (Author of The Last Unicorn) as well as many individuals from teens to elders.
If you'd like to learn more about it, you can go to www.gailstricklandauthor.com. Feel free to contact me via the website or directly at email@example.com.
Night of Pan is a mythic journey of the young Oracle of Delphi who defies her parents, the priests and even the Greek gods to save Greece from the largest invasion the ancient world has seen.
I look forward to hearing from you.