I had heard they are accessible. And as for stamina, @mousematt’s right, even going park to park, once you get to the backstage area of the second park, you don’t deal with any lines. Someone’s there to scan your tickets and off you go.
It is not front of the line access though, but it is a walking FP. And only good for attractions with FP’s, still at the discretion of the attraction CM. I was on one tour where the CM was close to cutting us off, just because we were going on 6 times in a row and they only had so many bobsleds.
100% worth it in my opinion. If you have the opportunity to do it, I say go for it, especially since you don’t RD (we don’t either). The guide might also have a much better understanding of operations that do accommodate someone in a wheelchair that the general public doesn’t know.
3 or 4 parks might still be rough stimulation wise, so I’d personally limit to 2 parks. But pick the ones that have the attractions you would have the hardest time getting access to regularly. That being said, I’d pick MK first, then HS and if you time it right, you can end the tour dropped off at FoP or one of the end of the night “shows” and any of the parks.