I went down the HT, RT route so can't offer direct experience of surgery, but it has came up enough times on this forum that I can summarise what others have said in the past. First thing is everyone is different and you have no idea how side effects will affect you. Some people go in perfectly fit and come out with no problems others come out with all sorts of complaints. This forum is very biased towards the problem patients as the people who come out with no problems get on with their life and don't come on a forum like this to seek advice and help.
I think most people would say: do hardly anything for the first two weeks, up to about six weeks build up to a normal level of activity (not your normal, just normal for a 64 year old), after six months probably start getting back to your normal level of activity (which sounds a bit higher than for most 64 year olds).
Throwing bowling balls around after major surgery is not something you will be wanting to do straight away, but hopefully will be something you will be quite capable of after a short while. It sounds like something which would be a bit of a problem if you end up with stress incontinence but will probably be manageable with pads.
If your surgeon has told you you will probably remain continent that is good news, but if you don't know already a surgeons definition of continent is not needing to use more than one nappy pad per day. Most normal people would not consider that to be continent, but hey ho! that's surgeons for you. If you didn't know that was the definition of continence then you probably haven't had enough information to make an informed choice.
Do you know if the surgery will be nerve sparing?
If the answer to ProSixty's question is "Yes, I will definitely need RT later" then you are being told they will remove the prostate and the cancer in it, but they will be leaving some cancer outside, which will probably continue to grow (and possibly spread to other parts of your body in which case you will have advanced and incurable cancer). The advantage of RT is these cancer cells outside the prostate can be zapped at the same time as the prostate, and hopefully get rid of all your cancer.
Nothing is certain with cancer. Four weeks of RT is neither here nor there and the side effects generally mild, though two years of HT would not be much fun.
If you go in to this thinking I'm young(ish) and fit and this will be a breeze, then you are going to come out the other side of this emotionally scarred.
If you go in to this thinking s**t, I've drawn the short straw and got cancer, but it's reasonably treatable, and if I am lucky I may be cured, and if not I still have at least five or ten years left and I can have a lot of fun in that time whether I am cured or not, then you will come out the other side with far better mental health.