I'd use the ISBAO standard as a starting template. If you get it through NBAA it is not that expensive. It certainly covers more than you need, but you can then pair it down to get what you want. Then when the time comes, you've got a good start on a legit SMS and ISBAO compliant document. You don't have to go the audit/accreditation route, but if you decide to do it in the future, you wont be starting from scratch trying to making your documents fit.