He wants to be a swinger

I have been dating a guy for almost a year and a half. I really love him too!

About 8 months in he has talked about wanting to swing when he gets married. I never thought he was super serious about it until one night I asked him if it is something he wants in his marriage or will he be able to give it up. He told me he didn't know. Well lately I have been having dreams that it ruined our marriage. I told him this morning that I would like to know by tonight. I will not hate him if he chooses to swing. But if he does I can't be with him. Am I doing the right thint? Any advice