Ok, how does this sound:

Dear Mr. Poopy Pants*,

Good afternoon! My name is Best Granddaughter* and I'm writing to you on behalf of my grandmother, Wonderful Lady*, who is a member of your facility. I just got off the phone with her and she relayed to me that she was recently told it was better if she didn't attend the weekly canasta game anymore. She is terribly upset, and at nearly 93 years of age, this has been her only source of social activity each week for several years now. The details of what happened are unclear (to me) and I was hoping someone could shed some light. I'd like to know what can be done so we can rectify this situation.

Thank you for taking time out of your busy day!

Best Granddaughter*
- Seek first to understand, then to be understood.
- Character is how you treat those who can do nothing for you.