My recommendation is to make your letter as personal to each individual as possible, They most likely know who you are. You have to tell them why you want them to be with you. Give details about BetterInvesting methodology and clubs you read about. The BI magazine has a monthly article of a club's operations and success or ideas to help them improve. Share that and emphasize the hold purpose of the club is to learn together so each of you can handle your own personal portfolio with confidence.