Thai Theravada Buddhism

In the temple where I am going to ordain, they often sit on their heals with toes bent forward (which I am working on) and they also sit with their legs to the side in what they call "mermaid style" which is very difficult for me. I am looking for suggestions on stretches and exercises to help me. I am 60 so these old bones and ligaments are telling me that they don't like these positions...they are very stubborn !!!