Happy birthday Wendy!
I haven't let my girls try coffee either, I'm worried they'll like it.
They both like to pretend they're drinking coffee or tea though.
Both of my girls have gone through spits and spats of biting, especially if they're mad, etc they will bite eachother.
I have just been really stern about it, put them in time out, and I stress that it hurts when they do that (basically give them the guilt trip). Once they realize they hurt eachother, they actually get sad and feel bad about doing it.
Honestly though, it rarely happens anymore. It seemed to be something they both went through around 18-24 months, and grew out of it.
At the time, they probably just haven't learned yet how to deal with anger and it seems to be the easiest and most natural thing for them to do.