QuietLion: I am a AARP member (you have to be past 50). I often choose the AARP-rate (with Marriott in USA it is often, prepaid 21-days, the cheapest rate, sometimes better than government-rates). Never did anyone so far ask for membership-identification at the hotel.

A good young friend of mine doesn't hesitate to ask for the AARP-rate - and has not have had any problem so far ...