Is there any pattern to Ben's hitting, Trudy? Is it the same child(ren), for instance? It's not at all unusual for kids his age, especially boys - they don't have the words or the emotional vocabulary generally to deal with their frustration, anger, jealousy, etc. Don't stress about it and don't deprive yourself of special time with him, better just to see if he can talk about it.
Loving how you're rocking Attack this time around, Trudy! (God, my children would cringe if they heard me talking like that!) Keep it up, missus. And I hope the foal's ok. xxx