Nipping & playing rough

Okay, last question I promise! We have 4 kids in the house ranging from 10-16. Our 3.5 month old lab (Koa) plays fairly rough with my 10 year old. We've tried to teach her to grab his muzzle like his mother would do but she's too afraid to do it and he just thinks she's playing even more. The other day while I was walking, he actually nipped at my calf because he wanted me to play (and I'm an adult!). He doesn't show any of this behavior with my husband but I worry that somehow he's getting the wrong message from the rest of us to be a nipper or ??? Any suggestions? He's a great dog, loved by all and probably gets wayyyy too much attention (did I mention 4 kids not including all their friends!). Thanks much for all your advice.

If you do a search for biting, you will find a few threads that people answered that question for other people with similar issue. I found them to be helpful. :D