A friend of ours hit our child - what should we do?

Neither am I, I was just pointing out that the fact that the man hit their boy doesnt means he would hit their girl.

Actually, we decided that our daughter will not be going to their house. They will meet at our house, or we'll use outdoor activities. You guys can call me a friendship traitor, a person who cannot reslove conflicts (and it's your right, and I'll understand) but it's the well-being of my children, and neither me nor my husband want them near people who cannot control their temper to the point that they lay hands on them. I do not feel obliged to seek them out and ask them why they did it, I know I won't be able to be friends with them ever again.
Thanks again, everyone, for your time and advice!

the well being of your children would be best served by you modeling good relationship skills, showing them how to resolve conflict, and showing them that attachments come with obligations. It is not saving a friendship that obligated you to have a conversation, it was the ten years, which you have blown off.

And refusing to go back around someone who's hurt you is a good model.

Modeling common sense is also an important aspect of a parent's role in a child's life.

I was at my friend's house with my two children aged two and six. My friend's dog big my two year old daughter in the face, totally unprovoked, just below her eye. My daughter's face was at his level and he just lunged out and bit her.
I left my son with my friend while I took my daughter to the hospital. When I returned, I was absolutely shocked and appalled to see the dog who bit my daughter still wandering around inside the house with my son (and her son, I might add).

I said, 'Betsy - why didn't you put the dog outside?!' snatching my son up and ushering him behind me before the dog could get to him too.
'He's never bitten anyone before,' she said and then 'It's cold and rainy outside.'
What the HELL!
I took my kids and left. She continued inviting me over to her house, but I just couldn't go. At first I made excuses, but finally I said, 'As long as you have that dog - I can't come to your house,' and told her the truth. Not only would I not bring my kids there, but I wasn't going either. I don't like dogs who are unpredictable and bite people. I wouldn't like people who are unpredictable and throw children to the floor in fits of pique either.

What if the next time he snaps with the next person that person hits his head and fractures his skull and dies? I can't tell you how many people I've met in prison who are in prison for many years for having thrown the wrong punch or shoved someone who fell and hit his head on something and died.

I called DHS on a mother I was working with on parenting skills when one time, right in front of me in a fit of rage she threw her one year old son on the bed and he bounced off the mattress and struck his head on the wall.
I'd never seen her do it before and I thought to myself, 'Give her a break - everyone snaps sometimes, but as a mandated reporter - I had to do it.
I didn't WANT to do it - I didn't ENJOY doing it - in fact I HATED doing it - but I had to ask myself, 'How will you feel if she does it again and the next time the little boy breaks his neck?'
Odessakit - I think you're making the right decision.
I had to do it, and I think you do too.

I understand completely. Sounds like the best solution -- you, the wife, and the kids stay in touch, but the guy won't be around your kids.

Avoiding contact with him will likely be difficult and incredibly awkward though.