Thanks for the reply :)
My horses are pretty calm personality wise, and they never really play rough other than some running around and threatening. My 25 yr old gelding is the alpha, but he mostly just pins his ears and pretends to bite when my younger mare gets too close to his food (and who could blame him, she's a vaccuum cleaner when it comes to food!).
I had not thought about the feeding issue, so it's good that you pointed it out. My two eat their grain separately, and are separated at night so that the older gelding gets his food (as I mentioned, he eats quite slower than my mare). Do you think it would still be an issue with the hay during the day? The only meal they really eat together is lunch hay.