Thank you so much for that teeter totter visual. It made me laugh!
And, to Coopcheney, it sounds like you've covered the basics: dirt/sand with plenty of grit, recreation, plants for shade and shelter (try patio umbrellas if they need more shade).
Logs are good perches, although they can sometimes attract ants and things if they are left outside too long, so we use cinder blocks. If your run is permanent, consider your soil type, and if you need to add some good-sized pebbles in order to keep down erosion and mud. Don't forget to provide enough drinking water, either. I'm sure your girls will love all that space and diversion!