You said...
Does this seem like a proper course of action?
Yes, external beam radiation is a very effective form of treatment and is particularly appropriate for men over 70 who tend to recover slowly from surgery.
You also said...
Is radiation painful?
Not usually. The actual treatments are usually accompanied by no sensation at all.
And then you said...
What are the side effects?
There is some tendency to get a bit of urinary discomfort (like a urinary tract infection) later in the treatments and problems with hemorrhoids are not uncommon, but both of these are generally minor and respond to treatments that his doctor will offer if they occur.
But the most common side-effect of any sort of radiation is fatigue. In my case it manifested itself as falling asleep while watching television in the evenings. Expect him to take more naps and give out early. This usually starts about
half way through the treatments and lasts about
a month afterwards.