Herecomesthesun I'm with you on the risk adverse thing! I love how my hair looks when I take the time to straighten it - but if I do it once a year that's a lot for me these days. I'm just terrified that one of the kids will be running around and bump into me whilst I'm doing it or that they'll get burnt whilst I'm cooling them down enough to put away!
In response to the initial question, I do feel 3 is perhaps a little too young - but it's none of my business unless the mother took it upon themselves to use the straighteners on one of my kids.
Re the sexism mentions: I have 3 sons (no daughters), all with medium length hair (for a boy) until a week ago when the older 2 decided for the first time ever that they were going to try a shorter style. So none of them really have a need to use them. Now that my youngest is now 5, I would consider doing it for them if, and only if, they asked for it!
Young kids love dressing up - there's nothing sexual to them about it, we as adults do that! 2 of my boys have asked me to paint their nails multiple times and for me to give them makeovers!!! So I did. Hubby went nuts - I asked him if he would have had a problem if we had a daughter and I had done it to her. He said of course not - so I pointed out what a sexist attitude that was and that it was JUST dressing up to them! They had a little bit of eye shadow, lipstick and the tiniest bit of blush. I wouldn't let them have the mascara they asked for on the grounds that I wouldn't have let a daughter at that age either.
So treat boys and girls the same, if they want their hair doing as part of dress up, why not, where's the harm?
I appreciate that got away from the original question about the hair, but I wanted to reply to the post about the fact everyone was presuming it is girl and remind people that as well as girls being able to do anything the boys can - but the boys can do anything the girls can too!