I really like the idea of writing a letter too (or maybe if they're Internet savvy you can try an email). I don't think it's really necessary for you to be there to read it to them if you're not comfortable doing that. As long as they find out through your letter what's really going on, that should be a great start. You should expect them to have follow up questions for you which they may want to ask you to your face. Or, if you want to avoid that, maybe ask them to respond to your letter with their own letter.