Nice to see that this thread has returned to civility, it was in danger of becoming a joke way too quickly... I would also like to point out that any SP who agrees to your request will likely have some additional security concerns, because she's putting herself in a more vulnerable position (no pun intended) than she usually might. So, if she ends up asking a lot of questions, don't be surprised - she's just trying to avoid getting gang-raped.
If you're willing to be patient, it might be best if you saw her solo first, just to establish a bit of trust, and you can discuss the details of the three-way after she has an idea of how comfortable she is with you. She'll likely be a lot more willing to do this if she already knows you from a prior get-together, and even more so if she knows you're not abusive or too aggressive; after all, when men get horny, they sometimes push too hard, and might be inclined to be even more aggressive when there's another man in the room. Just be sure to take the SPs concerns into account when setting this up, you'll have a lot more fun if she's not concerned for her safety.
For my part, I don't think I'd ever agree to see two brand-new clients at the same time; too many things could go wrong, and unless I know the guys pretty well, it could be anywhere from awkward to dangerous. On the other hand, one of the reasons I love doing duos is because other female SPs can enjoy certain things that are normally reserved for MMF threesomes; a MFT three-way has so many unique possibilities! ;)