Hi Beth, a fellow Houstonian here…
I wouldn’t overthink it, jump on it and you’ll have the time of your life… Typically people with very different levels of fitness and endurance join these rides, but after a few miles the big groups will split into more manageable smaller groups of similar skill, so it will not be as overwhelming as you may think.
Riders in the area are normally very safety oriented, I’m actually learning to ride safer since I started riding groups… So I wouldn’t worry about this either…
I’ve started doing group rides about 9 months ago, and I wish I started earlier… You’ll find great camaraderie, and likely you’ll want to do group rides regularly in the future…
Edit: I think I may know your husband (Ch… ?). I’ve done a VCC Century Ride with him in May, small world if I’m right 