First understand that you are just lucky to be able to interact with the women. 9/10 it is going to be about them, you are lucky/special enough for them to include you in their fun, if you have that attitude it should work well. The women can outlast you, keep this in mind and use it to your advantage. Make sure there is lots of 4-play to make sure they do not notice your limitations, it does not matter if you can go for hours, if they are willing to go that far they are going to go your time +. So make sure they are well stimulated before you start in on anything. Include some toys in it, that way if someone can not wiggle in somewhere they can still be stimulated other than just hands.
Hopefully you have women who really like each other and are not jealous of each other. Everyone has to share everyone else for it to be fun and natural.
Oh and make sure to say thank you at the end and give each one a kiss so that they know you appreciate being a part of it, this will ensure that you are thought of as thoughtful and invited to play with at least one of them