I encourage you to think about the idea that being both Christian and Jewish spans a huge spectrum of beliefs and practices. For instance, your son is almost by definition both, in terms of cultural heritage. Some of us born into interfaith families will choose one primary religious affiliation but continue to honor a second one. Some of us join two communities (one Jewish, one Christian) with progressive and non-exclusive theologies. Some of us find one community (such as an interfaith families community, or Unitarian Universalist community) that supports us in staying connected to both religions. And some of us, especially in the millennial generation, have no interest in formal affiliation in either religion but continue to find meaning in the ideas or practices or cultures of both.
You do not mention Dad’s Christian denomination or the denomination of the camp. I would explain to your son that if he declares Jesus as his personal savior and affiliates with an evangelical Christian denomination, then that would be a choice of Christianity and a move away from Judaism. But if he wants to learn more about Jesus as an inspiring Jewish historical figure, or about Jesus as a metaphor in some of the more progressive Christian denominations, this exploration could be compatible with a Jewish (or interfaith) identity.
Remember that Pew Research has found that many Americans change religions more than once in a lifetime. As a parent, I would want to determine to what degree your son’s new interest could be based on peer pressure, or evangelization, at camp. Of course, peer pressure can also be a factor in wanting a Bar Mitzvah. I do not believe it is wise to put artificial deadlines on interfaith children to choose an identity (for instance, by the time of Christian confirmation, or by the time of Bar Mitzvah). For many of us, integrating our complex religious identities is a lifelong process, a process that can be joyous as well as challenging.
I think your best course of action is to encourage your son to continue his exploration, and try to offset any external pressure he may feel to choose one religion, at this tender age. I will say that bar mitzvah preparation is an excellent opportunity to further explore his Judaism. Both of my children benefited from this process.
Susan Katz Miller is both an adult interfaith child, and an interfaith parent. She is a former Newsweek reporter, and the author of “Being Both: Embracing Two Religions in One Interfaith Family” (Beacon Press).