Its a hard one. Because it's definitely easy to say you'll do it... and and when it comes to doing it.... it's easy to freak out.
I recommend not doing it until you're absolutely sure that you're comfortable with it.
Or even have a safe word to end the whole encounter.
I find watching my husband with another person hugely arousing. Watching another person being satisfied by someone who's mine..
On a page like this it's good. Because it's not a couple you know well and Are close friends with. So you don't have to encounter with them again if you choose not too.
I like this page because people on here don't take offense of you're not interested etc.
Happy swapping x