I like the letter. You state your points clearly and it also has a very friendly "tone".
A small grammatical note: When using the word "Michigan" in a letter, one uses the word "Michigan" or the abbreviation "Mich.". Officially, the only time that one uses the postal abbreviation (MI) is when addressing a letter.
Just a question, not a criticism. Do you really want the company to receive a large number of letters that all look the same? I know a few people who work as aides for elected officials and if they receive a large number of letters that look like they are a form letter, they just toss them. Don't get me wrong, your letter could certainly serve as a model of communicating effectively. However, IMHO, if some who wished to write to the owners were to write their own letters too, it will have more of an impact.
Just a thought and yes, I will send them a letter this weekend.