I finally set up a pen for all the puppies and the two mamas. Boys in the left corner, girls in the right. I originally had a divider to separate the two mamas. That didn't work because Sierra could figure out how to get around and/or over the divider so I took it away for everyone to be together.
But then Sierra decided all the puppies were hers which left Cheyenne with out her boys.
It just didn't quite work out the way I'd planned so they're now in separate pens again. The puppies get together, without mamas, a few times a day to play and eat each others faces.
Hopefully when they're weaned the mamas will be a little more accomodating and will allow one big party.