Yeah, I'd definitely go with 'Mr.'
It is correct to call a lawyer 'Dr.', but that's pretty pretentious.
Here in New York, it has been held to be unethical for an attorney to hold him/herself out as Dr. So-and-so if that individual does not possess a true doctoral degree (M.D., Ph.D., et al.) I'm not sure I agree with that Ethics Opinion, but it is what it is.