We had previously borrowed their some car some, more informally, and reimbursed them approximately based on what it was worth. The main change here, though, is moving to a system where we can use the car without asking first, which is pretty useful to us.
Yeah. Thinking about it more, if you assess the probability that they ‘defect’ with your money as low (‘you know them well’), then you’re coming out ahead over renting the car from them at 56 cents a mile. I just recommend you at least text or email the details of this agreement and make the payment via a traceable means. Not the same security as notarized with multiple attorneys as witnesses but good enough for this transaction. (or to provide evidence to support your side in small claims)
They reviewed a draft for this post over email, which seems reasonably close?
Probably. Main thing is to not have any agreement backed up by “I thought you said...”. It needs to be written, and specific, and make a small claims judge think there is at least a 51% chance it’s true.