I’m not a doctor but my family of four went. My son was sick at the time (we didn’t know) and I suffer from vertigo and was a little worried that it would affect me. None of us got elevation sickness at all. But we went with a trained guide who limited our time there to lessen the risk. He I dictated people tend to go and hang out which increases the chances. I think he said not to stay more than 30 minutes? We saw people who were definitely sick so the risk is real but you will never know unless you try. And stay hydrated!

I think you should call the tour company and ask them if dogs are allowed.

There was, I don't remember the exact number though. If you want to make sure the tour actually happens and there are enough people, you can always call the company couple days before your chosen date and they will tell you how many people have signed up.

We only had to wear masks on this tour when we were inside the bus. Otherwise, Denver was mask free.

We stopped at Manitou Springs for lunch, however, I would recommend still packing some snacks for the road.