Daniela and I play alone and have no rules. Since we are now within a closed group of married couples, it is easy, stress free, and frequent. It allows for us, all of us, to have more sex and more sexual variety. In many instances the primary benefit is that one of us can watch the combined kids while the others play, then switch off. We have also gone on long weekends and vacations with others in our group.
I agree that there is fun in playing while your spouse is around, but we don't have to watch one another fuck all of the time. Plus, there is nearly as much joy in "bringing it home" and reclaiming with one another after whatever happened has happened.