Interesting. While we're not exactly swingers, it seems to me that among the two guys and three women in our poly family, it is the women that are keeping the sex life spicy. The guys used to be more into play and variety, and while they still like their fun often (extended foreplay then fucking), they're not as into threesomes and MFMF as they used to be. Even after the three of us women had children and moved into our thirties, our sex drive has stayed strong and increased. We women take our family and professional responsibilities seriously, but when the mood hits us, as it often does, some other responsible person can watch the children for an hour or two while we enjoy the sexual side of life. (Perhaps part of it is that the guys take their family and professional responsibilities even more seriously, as well as keeping in good shape physically. They stay looking good by working out hard, a mix of running, weights, biking, swimming, which tires them out. We woman do it by more moderate exercise and eating much, much less.)
At this point, I think David and Red could be satisfied being monogamous with one of us woman. None of us women could, especially because of our loving bond to each other and our strong Lesbian side. We also share a boyfriend on the side (a married guy whose wife knows, but doesn't participate; she watches the children.) Anyway, a long way around to saying that these three approaching middle-age women are the ones "actually have the desire / ability / confidence to actually make [our form of] swinging a permanent and fun part of their lives."