Nice composition. As has been mentioned, a longer focal length will help compress the distance between front and rear rows; I think that an image where everyone looks the same size would look better. Although remember this wide angle exageration; it can be used interestingly with children, pets, single subjects, etc...
The folks in back are just edging out of the DOF; they need to look as sharp as the folks up front.
Clothing coordination can make the whole thing come together. Darker toned clothing helps focus attention on the faces. Logos and writing can be very distracting.
The couch and close background make the image look very casual. This isn't right or wrong, but if you want it to look more "professional" I think you have to hide the couch (background colored blanket over it), or sit on something else that doesn't show in the pic. Studio backgrounds are almost as far away from the subject as the camera is. Close backgrounds, particularly indoor walls, can look snapshotty; somehow you have to give more interest to the wall if it is going to be so close to the subjects.
This lighting is great for color, and there are nice catchlights in everyone's eyes, but it's so diffuse that there are no shadows at all. This is where a black "reflector" (blanket, paper, post board, whatever as long as it's dark) might come in handy. Hold it up just off one side to keep light from reflecting back on that side, adding a little shadow, and a little drama.