Hmmm...I'm 47, and I'll be checking myself out of the "home" to take my family to WDW in 17 days.
Actually, I'll try to answer your question seriously since I had those thoughts myself a few years ago. A mom goes through so many years of not riding thrill rides...first you're pregnant, then you're with a baby, then you're pregnant again, then you're with a baby and a toddler, etc. I wondered if I would be willing to ride thrill rides once my own kids were old enough to ride them.
We went to
Disneyland 2 years ago and I told myself that I would ride everything, and I did. California Screamin' freaked me out at first - I didn't think I would like being upside down. I closed my eyes the first few times, but ended up loving it.
As for rides we don't like:
DH ("only" 46) won't ride the teacups, but he's never liked those types of spinning rides.
I am very headache prone, so I try to avoid rides that bump my head around a lot. (The worst ride in the world for me is the log flume at Sea World in San Antonio...the ride UP to the big drop is so bumpy that I have a headache for the rest of the day.)
Have a geat time and don't worry about your parents' advanced years. I know that when I was a kid, my mother (who grew up in the depression and never had a "childhood") would outlast us all at the Disney parks.