I think the OP is pretty well addressed, but I’ll just chime in to say that I’m in my 30s and my friends and I still tease each other about things. Race gets brought up very rarely (and only if the joke is simply too good to pass up), just because it can still be a sore subject. But I’ve been teased about being half Irish, being short, and being ~10 years younger than some of my friends – likewise, my best friend is 13 years older than me and I tease him about his age sometimes (he’d probably say all of the time, but he has memory problems ;)).
Hell, I used to tease my cat about not having opposable thumbs. 
A few years ago my white cousin married a black guy, and the music at their reception was eclectic. At one point we’d all been out on the dancefloor rocking to some 80s nostalgia, and a rap song came on that I didn’t really know – but, being in the flow, I just kept right on singing and dancing. Well, the chorus was something like “fight the power,” and at one point my cousin and I made eye contact: there we were, a couple of white chicks, with our fists raised and singing “fight the power!” At that moment we both realized what we were doing/saying, and nearly fell down laughing. 
Huh … for some reason I’m more comfortable with the idea of kids teasing each other about stereotypes than I am with them using racial slurs. No idea why, it’s not like one is inherently worse than the other. I didn’t even realize I had a “preference” until I read your post!