I'm in a position to start a "relationship" with two woman.

One girl(say trish) is someone who has known me for many years and knows me very well(we have had 3somes in the past). she is very excited about the idea.

the other girl(say jen) is some one who has never had a 3some, but worships trish, and is very receptive to the idea.

I have never met jen, but trish is so eager for us to all get together; and my game is so tight, its somewhat a given(although you never say never)

"The challenge" is in getting them to get along; or policing them. from my experience with two women; one always tries to be number 1. I would like to avoid any kind of abuse between them.

If done well, we can all move in together, and live that life

SO, how do I get them to put in a team effort?
any "real advice" guys(might need a expert for this)