I get it. You are asking for advice on how to best approach your husband but you fully intend on communicating with him at some point. You need a way to first determine if this is a safe topic to discuss before launching into an open discussion about it. Knowing this is a very common fantasy in men should give you hope.
I believe the folks here could provide excellent advice on how best to start this conversation since many here know how it was first broached in their own relationships. I see men asking for advice on how to “trick” their wives into it. I bristle when I see those.
Our own foray into this grew organically from nudism to light swinging, to swinging, to me watching while she plays. we had no goal to wind up here. the journey has been great and everyone of those steps could have been a successful end point.