The question isn't "should they" but whether or not they want to. If the answer is 'yes,' then I'd be asking myself why? If it's mere curiosity, but your love is strong and you want to remain together, then perhaps you would tread lightly forward. I think it's probably a recipe for disaster, but I guess you never know until you try.
I think there are a lot of considerations though. For example: Who would you swing with? Strangers or people you know? Does one of you already have someone in mind? If so, who? And is swinging an excuse to cheat, or really just based in curiosity?
Are both you and your partner equally interested in swinging, or is one more interested than the other?
What are your intentions regarding safe sex?
Do you know the difference between swinging and an open relationship? Are you always swinging as a couple? If not, why not?
Only after you answer these questions, and more, would you have a true idea of whether or not this might be right for you. I've heard that it really does work for many people. But it destroys at least as many more.
Tread lightly and best of luck.