The family doctor letter would probably only be ok if you shadowed him. I got a letter from a MD I work with, and I received my first acceptance, from DMU, today.
It's perfectly acceptable. Just make sure you meet with your family physician and/or present him with your CV and/or shadow with him or her for a short time.
I don't see how using a family physician would hurt you. That person has presumably known you for a lengthy period of time...
Letters that do not count toward completion of your admissions file include: letters from relatives, spouses, family friends, coaches, personal trainers, veterinarians, dentists, your family physician or pediatrician (unless you have shadowed or worked with the doctor). We prefer the authors are as objective as possible.