The tours are not very difficult. Places like Persepolis require a little walking, but not a lot. Since you will have your own vehicle and driver, there are not many physical demands.
Some hotels may require going up a flight of stairs. Let us know if that would be a problem, and we will do our best to book you on ground floors.
Some of the tours do have quite a bit of time on the road, but that is not very strenuous, since you have your own driver. You will not have to do any physical activity that you think will be beyond your means.
We can discuss any physical concerns with you before you book your trip and determine what is the best itinerary to suit your personal needs.