Let's see, facial features...
The lady looks around 40 years old quite a bit older than the guy because of the lines on the cheeks. If you want her to look younger, perhaps the lines could be closer to the edges of her mouth and a bit shorter? For dimples.
edit: I am terrible at estimating age, don't take my numbers very seriously.
The dark shades above the eyes make them look a little sunken in. Not sure what to do about that.
The skin area inside the beard looks like it has banding/pillowshading with the shadows lining the edges of the beardpatch. Might be better to just aa one pixel at the end of each line-segment forming the curve.
Maybe try a little bit of line at the edge of the stache-area for a stronger smile.
The shadows around the guy's eyes work in my opinion, so I don't think there's a need to change them. At least for now.