I have not read all the replies, but heres mine. I have three boys7, 4, and 2. I dont know what the magical age is. Actually, I feel there is no right age, but appropriateness based on each childs maturity and the situation. We go for the family restroom whenever possible. DH always takes them to the mens restroom if he is there. But when there is no family restroom or DH isnt there. Its tricky.
There is no way in hell I would leave DS7 standing in the mall or a department store while I used the womens restroom. Hell be coming in with me, thank you. Lets not forget Adam Walsh. He was 6. Most victims are in the littler older age range because they dont have the maturity needed and parents let them out of sight because they have to grow up sometime. When I use the restroom, DS comes in the stall with me, and turns around. Not that he would see anything, but that leaving out is still leaving him vulnerable.
As far as letting him go alone
depends. His elementary school does all school skates. Its only his school at that time. Most kids (K-4) and moms; there are a few dads, but not many. I keep a close watch on the door, but he can go by himself. At the mall, sorry, he cant go alone. Ill let him go into a stall by himself and stand just outside. If we both have to go, we go in the same stall. I cant help but always thinking of that little boy (wasnt he 9?) who was in the mens restroom with his aunt standing just outside the door when some man came in, slit his throat ear to ear, and walked out. After 10 minutes his aunt came in looking for him. Too late. There was another restroom thread on here a year or so ago and someone, with a better memory than me, was able to provide a link to the article. It was big news at the time.
Call me over protective, but well never know. Millions of people drive around every day and are never in a car accident; does that mean we shouldnt wear seatbelts or use carseats? No. Its because you never know when it will be you. My sister used to leave her keys in the car all the time. She would leave her house unlocked during the day. She left her garage unlocked all the time too. She doesnt anymore. She was at someones house (extremely nice neighborhood) talking to them at the door; someone stole her van. The police recovered it three days later, crashed, and completely stripped. The next month, someone went into their garage at night when they were sleeping and stole everything but the cars. And the chief of police and an FBI agent lived on her street. She now realizes it wont always be someone else.
I love your response. Its calm, cool and direct. I really think women who have a problem with
little boys (were not talking boys going through puberty here, but kids that are still more oblivious than not) using the womens restroom with their mother, have their own hang ups. At our last trip to WDW, I dont know where DH was, I took DS7 (then 6) into the womens restroom. When he came out of the stall, I told him to wash his hands. I was washing mine for some reason and he was standing next to me. I told him again to wash his hands. He said he did. I said then he must not have done it right he did it so fast, so do it again. He groaned and started to do it (again?). The older woman next to us smiled and told DS that one day he would be thankful that his mother cares enough to teach him right. She had no issues. I dont run into many that do. I see little boys in the womens restroom all the time. Oh my gosh! They see women washing their hands and stall doors. How traumatizing.
Anyhow, when you feel comfortable, when you know your child can recognize dangers, when you know that theyll wash their hands properly, is the right age. Or the start of puberty.

Peoples views probably depend on their environmentnot that it changes safety. Criminals dont usually live in the nice, expensive neighborhoods, but that is where they rob. Someone who lives out in the country in an extremely small town are certainly not going to feel the same way as someone living in one of the five largest cities in the country on this issue.