Although there are many great senior fitness instructors in this forum (and I’m sure you will get some great advises), I would also recommend for you to contact Guy Andrews. He is the founder of Exercise ETC. and he is very knowledgeable when it comes to seniors. I recently attended one of his workshops where he covered a lot of great information, especially regarding exercises and routines for seniors. You should be able to contact him through his site:
I hope this helps.