Questions, but not so many answers

I am 65 and have been looking into bariatric surgery for 4 months. Originally, I wanted knee surgery, but my surgeon said my BMI should be 40 or less. I am around 44 right now. I decided it would not be a bad idea to have bariatric surgery first, to ensure success with the knee surgery and have been on that journey ever since. 

I have attended 3 of my 6 mandatory pre-surgical meetings, plus have had several of the pre-op tests done to assess my general health. I have been sold on the VSG surgery from the very beginning, but my surgeon wants me to go the RNY route. I am not a fan and recently have been told horror stories by people who are 8 and 10 years out from their surgeries. If anyone can give me guidance on this issue, it would be appreciated.

I am told there are some concerns that older people have that younger folks do not face, but I can get much specific information, so if anyone wants to post articles, videos or websites that address this issue, that would be very helpful.

I also struggle with the concept of vigorous exercise. Being older, I am moving more slowing and enjoy life that way. If people can contribute realistic workouts for seniors to do, that would be great. Right now, chair yoga is my first choice because walking is tough on my knees.