I let my boys go into the men's locker room together when they were 8 and 10, maybe 7 and 9. Since I used to let them swim after I taught an aerobics class, this would be their reward for having to stay in the child care room. One time, they were taking a very long time in there, when the superintendent of our school system came out. I asked him to go back in there and find out what the heck they were doing! He reported back that Scott was blow drying his hair and I shouldn't worry. They were really mad at me for having the school superintendent check up on them, but they lived.
I remember feeling very uncomfortable when I was pregnant, in the locker room, with little boys staring.