I asked this exact quesiton to AMA Headquarter about 5 days ago as I wanted to put on an event where non-AMA members could try RC flight.

AMA's HQ response was, if an AMA member uses thier own equipment, i.e., radios, trainer, etc., they can give one flight to non-ama members on a buddy box. In such cases, the AMA feild and AMA individual insurance is still in effect. I'm satified with who I talked to on this issue becasue I have a paper trail (email) from the AMA on this issue. However, you may wish to confirm with others before you host your own event. Cheers!