Large quantity of piping icing

[VagueButlmportant]

I'm organising a fundraiser on Tuesday and one of the activities is to pipe and decorate a rudolph gingerbread man (upside down gingerbread man)

I have baked the biscuits and bought some disposable piping bags, but I'm wondering how best to make the icing.

I have a kitchenaid or a hand whisk. Does anyone have a foolproof way of making large quantities of icing to the right consistency? Could I make it ahead of time and take it in a plastic tub?

Also what is the best type - water / royal?

Thanks!

for school biscuit decorating, I always do water icing. I don't make too much at once, and I make sure the piping bags have VERY small nozzles so kids don't squeeze too much out. then it lasts a long time.

Thanks Parietal. That's great.

I have a habit of making icing too watery, so I'll have a go beforehand and see what ratio I need.