The advice I'd have to give, which would be pretty similar to Jenny's comments, is that for arm hooping you must make sure the hoop is lightweight. When I was teaching my grandmother-in-law, she was taken back by the wrist pain because the hoop was a 1" 160psi.
Also, not showing off also seems like great advice from Jenny. I did so and, just as she said, my grandmother exclaimed, "I'll never be able to do that!" ... definitely lessons learned.
I had my class and the advice about the chairs and the lightweight hoops were great. We did 1/3 of class in chairs with arm hooping and coordination, did 1/3 with waist hooping and reversals, then used the wall to do stretches and re-introduce them to some slow spins of 1-2 revolutions using the wall to steady them if they got dizzy or wobbly. And of course, they just wanted to talk some for a while as well. I always make it a habit to not pull out the tricks for any of my classes up front because of the 'intimidation' factor. As a student myself, I sometimes get inspired by master hoopers or yogis but what can happen on occassion, is that I get really psyched out and just feel it's impossible. Thanks everyone for paving the way!
This is an excellent thread with such great information. I haven't taught a ton of seniors yet, but my mom, who is 65, is starting a Grandma Hooping group in her local area, and I look forward to passing on all of this info to her. Thanks y'all!