I am a strait female who had a threesome with another strait female. If the man is the focus point of this adventure it seems quite easy. The Mrs and I didn't get wierd when our bodies touched, we shared our "victim" well.
It was wonderful for Dog and I enjoyed making him the center of our attention.
Two women in one bed does not have to mean that bisexual play is needed nor that the fun wont be as much fun if there is no girl on girl play.
I say give it a go. If the females in question are ok with being in the same sexual situation then why not?
Your friend,
Prettylady