Whenever you add another person, always chance for more issues i.e. cancellations, lateness, etc. So few tips:

1) I would do it as an outcall where you can get the room, get settled, get showered, etc and have the girls come to you. Pick a place that is parking friendly and not a high traffic area. A suite is great if you can swing it.
2) Book at least two hours for the three of you togther. One of them will proly run late and you want to get the max out of this experience
3) See if you can find out what limits each girl has before hand. Some women are really bi and some are "pay for gay". If one girl really isnt into it or has a ton of limits, you might be really disapointed and it might turn the other girl off.
4) Start off with some alcohol. Believe it or not, even many seasoned escorts get nervous and some champagne and maybe some light appetizers awiting them is a great ice breaker for all three of you.
5) You might consider having the girls have a phone chat before hand. That breaks the ice in a big way and gives them a major comfort level with each other that may take an hour into your session to establish. Good luck!

makes for less condom changes.

which is good because the two gals have to be very compatible for this to work.

Otherwise, get plenty of rest and be well hydrated, and eat your Wheaties.  Double take a bit of physical work.

I do not recomend any alcohol as that dulls the senses and adds to fatigue.

Done properly, doubles are a wonder time.

Let us know how it went.

of yourself several days before the date. Get plenty of rest, eat the right foods, plenty of water for hydration, etc.

Relax and enjoy because the time will fly by.

I would definitely consult your provider as to who she likes.  That's more important than anything, honestly.