One of the most important things to keep in mind for any post surgery situation and particularly for the shoulder, is to start very small and light and progress slowly and regress at the first sign of an issue. Always get clearance to work with surgery clients. Follow recommendations to the letter. And ask for quidance as much as possible.
If all of the above are in place, a complete evaluation of the client would be wisest. The more and better you understand the “whole” client, the better job you will be able to do in helping them.