I would like to set up a session with two female escorts which involves them with me as well as each other. My question is would it be better to have one provider bring the other or inform two separate girls of my plans and see how the evening goes.

Wow, lucky you, dan69er2,
Yummy! First, I'd suggest going through the TER review search and checking to see if either provider lists doubles as one of her functions. Then, I'd call each provider separately and ask  if she's got a favorite. Some providers have a "special girlfriend" who may not be listed on TER. Others have arrangements with other TER listed providers and they prefer to double up with those only. Also, one provider could have something against another, for whatever reason. You need to be sensitive to those issues. Go ahead and call each provider and ask if she's got someone in mind. If she doesn't, ask each one to check out the other on TER. Your biggest problem will most likely be how to find a mutually convenient time for all to paarr-tay!

Have a great evening,
the Love Goddess

Some agencies have two escorts that are willing to do a double.  Usually, they'll only double with each other and not other girls in the agency.  So try searching agencies that have a lot of providers working there.