I just wanted to share some of the things that I learned from biofeedback recently.
My toddler has never had surgeries, but still has internal rotation. We are trying to strengthen the infraspunitas muscles and the rhomboid muscles. We found out that the best exercises for the infraspunitas is swinging on an adult swing (the kind where they need to hang on and maintain their balance) and climbing ladders or playsets. For her rhomboid muscles the best exercises were crawling and reaching into her back pocket.
Since we are located in a cold weather area we have installed a swing (on a 350 pound strong chin up bar) and climbing area in our house. I hope this can help someone else.