You might be surprised at how supportive the docs are about biking. "My" docs have given me no trouble with my bike commuting. If they do, you could always look 'em in the eye and firmly announce something about preventive medicine.

Also, when you state that you are doing something - however wierd - for Lent, people tend to back off. After that, they'll be used to it. At least it's worked that way for me.

Finally, I agree with everybody else. Don't try to set any land speed records on the one-mile ride. A walking pace is fine. You are talking about walking the distance, after all. You can take your time and smell the roses, and you won't end up smelling like the fertilizer. (Did I just type that? )