Well, you rarely plan a snowball fight; in fact, it's more often a snowman build that gets out of hand. My little piece of advice: start with the fight to avoid tears if the snowman suffers collateral damage from the battle.
So to have a snowball fight, you need snow and a pair of gloves. Yes, you were right to come and read this tip. Sorry, I'll keep going. So, as well as snow and gloves, you'll need to bring a scarf or hood, because snow sliding down your neck is unpleasant (sorry to bring back this good memory). A little tip for encouraging kids to wrap up warm: tell them that their ski suit and jacket will cushion the impact of the balls coming their way.
Then you need some land. You know what I mean: big enough, with snow that's not too hard, no gravel or pebbles, and a few hiding places. And if you have an abundance of snow, you can even improvise building defensive snow walls.
Finally, a few rules are in order. Saying that, the only one you'll manage to get heard at first is "NOT THE HEEEEEEEEEEEAAAD!". Then you can suggest others. But first...
HikingGears tipsTips for beginners Practice TipsFamily, babies & childrenSnow & cold weather Where to go ?Hiking responsiblyNature Explore