Use a 5-gallon bucket of sawdust or stove-pellets for pee, use the toilet for solids. Remove the toilet handle and put it where the adults can find it.

If you really did need to use water from your pond, I wouldn't plan on chopping through the ice every day if I didn't have to. I would open a hole and transfer water to a water trough either in the barn (if you have enough animals to keep the temperature higher than outside) or on the porch, out of the wind, with straw bales packed around it, with some sort of insulation on top (more bales?).

I don't know the temperature limitations, but livestock people will chop a hole in the ice of a horse trough and drop a football or tennis ball into the hole. The wind shifts the ball around and prevents the hole from freezing up again. They say...