Yeah, I agree with everyone who says to get him to stop being a female dog. What is their beef with doing squats? They should at least be able to put some light weight and get the form down. If it's a problem with the bar hurting their upper back/shoulders/traps, get one of those pads that go over the bar.
Same with lunges, light weight so they can get comfortable with the form, and then start upping the weight.
As for another exercise that targets the glutes, the leg curl machine where you lay on your stomach, and the hip abduction machine (the one where you sit in the chair and open your legs that works the outer thighs) works the glutes secondarily, I believe.