knitcook - check out www.collagevideo.com, and search for beginner or beginner/intermediate workouts. You’ll find that you have some options which aren’t Richard Simmons and aren’t with super-athletes either. I chose Aerobics Only, Beginner/Intermediate level/floor aerobics and got 37 matches.
I’m thinking of getting my mom Pick Your Level: Fat to Firm Fast, since it has a beginner option, as well as intermediate and more intermediate/advanced options and she can follow the beginner option as long as she needs to. The instructor, Michelle Dozois, often has a variety of body shapes represented in her background exercisers.