I understand the points made by those advocating the banning of snowball fights on the grounds of potential risk to health and safety, but if society takes that route, by the same token, we should ban many other activities.....
Swimming in the sea is highly dangerous, you might get stung by a jelly fish or caught in a rip tide, playing rugby or cricket is dangerous, you might get tackled and injured or hit by a ball, climbing mountains is risky, you might fall and break a leg and need to be airlifted to safety, going for a walk in the countryside you risk tripping on a tree root or being stung by a wasp. We’d have to ban all sports, and even ban embroidery in case people pricked their finger on a needle.
Before that, we would need to ban driving cars and motorbikes which are far more dangerous than most sports and pastimes, Whatever you do, don’t get into a relationship with anyone, far too risky for your emotional well being,
If we took this attitude to its logical conclusion, and banned every fun activity that poses a risk, we would all end up staying indoors wrapped in cotton wool and just watching animated adventure films for entertainment, (thereby risking our health because of lack of exercise).
Of course, there are certain activities that pose too high a risk which should be banned, and others which need to be regulated or for which formal training and qualifications and safety equipment should be required, but if we eliminate all risks, life would not be worth living.
We teach children the rules to follow when playing in the sea or riding a bike or playing football; the same should apply to snowball fights. Teach children how to check the consistency of the snow, not to play where the ground is stony, or near buildings and vehicles, and not to throw at someone unless they are a willing participant in a game. Wear sensible clothes and a hat, don't aim for the head and have a reasonable distance between teams.
In other words, have fun but minimise the risks.