It''s a difficult situation you find yourself in, hoping to have your image(s) re-touched without hurting the feelings of your photographer friend who took them. If you were to go behind his back and he later discovers it, assuredly he will be annoyed, hurt or miffed since you went behind his back; additionally, he'll feel you tampered with HIS work, and do remember, that the person who takes the photo is the artistic owner as well as rightful patent holder, too.
Your friend will be pleased to hear that you liked them, and perhaps you should make it clear that you do like his work, maybe ask if you can recommend others to him (family members, friends, etc). In the same conversation, using utmost subtly, you might suggest that it was suggested by others that you have those very nice images retouched to lighten or eliminate the obvious blemishes, and ask what he thinks about it. Regardless of what he responds, thank him and do not hold a grudge against him. Artists are often somewhat sensitive and some even temperamental about their work, and photographers take pride in being artists (some more than others).
It's admirable that you care about his feelings. Here's something for you to consider: he may have left your images untouched for fear of hurting your feelings about your appearance. So, it's OK if you speak with him as a friend. Good luck and best wishes.