Truly, that could be loosely described as soft swinging although that does usually involve swapping for most things stopping at intercourse. If you are to look on the many sites you should probably look for couples into (SRF) same room fun, but even then you would need to be specific as to what your rules are.
We can't stress enough that you and Mr.S are absolutely clear with each other where you draw the line, and make that crystal to anyone you contact.
A word on contact sites. They are absolutely full of time wasters, weirdos, liars and very screwed up people. Be careful, and take care what information you give out. If you go on as a couple you very often get hit on by single males trying to engage you in cybersex whilst posing as a couple. You can call their bluff by asking them to both appear on cam on MSN. When a guy appears and says his wife is in the bath or something just tell him to piss off!
There are parties you can attend where you can do your own thing and just be watched, or just watch others, but expect to be asked to participate in some way. Google "radlett parties" to give you a flavour of the scene.
Either that, or do it in a room full of mirrors, it'll look like you're at an orgy LOL!
Hope that helps. The Naughties.