just saw this...WOW a lot of replies
frankly we can harp about about minors and all that, but my tuppence to the OP...
fine, my only consideration is that a kick in the balls isn't gentlemanly
however, he got what he deserved. the daft sods were up for annoying someone and bit off more than they can chew. Also throwing snowballs at someone carrying electronic equipment is potentially damaging to personal properly..which I think you can reasonably defend. Secondly he swung first and made contact. so it wasn't a feint etc. he was squaring up to hurt someone. so go ahead. kick him in the balls. the police have more important things to worry about and would have done sod all about it tbh. what can they do to 18 random kids on the word of one person after the fact. During the fact the OP made one snotty kid (not a minor though, he knew exactly what he was doing) you can drive at 17 and get married, so your actions are you own!
for Chaz...you can rise above someone and in a perfect world...this would be great.
but a dozen or so 18 y'os aren't going to learn from that and would just pick on someone else. If they'd done that to a granny she might have fallen, broken her hip, been too scared to venture out in the snow again.
From a reasonable self defense point of view, he was hit once..he hit back once. He didn't employ any weapon (improvised or not)
and didn't break anything or do any (that we know of) lasting damage.
so Stan...I hope they didn't ruin your day too much....and I hope you ruined his a fair bit.
if the police do become involved, good luck and be reasonable, considered and factual in your recount of events.