Hi Becky,
We have two Pekin drakes in a 10x10 enclosure, soon to be 10x20, and for now, we do use a baby pool. However, my clever hubby decided to save my back and this is what he did:
He put several half cinder blocks under the pool, at equal distance, and level. Where the ground wasn't level, he stomped them in a bit.
Then he put small pieces of plywood on top of the blocks, to create an even holding area for the pool, so that no edge of the pool hung off (believe me, we went through several fills and re-fills to get it even, but it was fun!).
Then he installed a simple drain off to the side by the temporary brick-ramp they have in the pool.
PVC pipe and a PVC shut-off valve connected to a long 1 and a quarter inch PVC hose (left over from a well we had), that runs into the woods.
It runs up under the fence, but it settled into the ground a bit so the fence is not to propped up.
Voila! I now have a drain and while my precious ducks graze, I drain the baby pool by simply opening the valve, basically pressure washing the sides and bottom of the pool (like rinsing out a very dirty bathtub, chasing it all down the drain). Once or twice a week I have to hand wipe the sides, but that is very easy. Then close the valve and fill it all up! 
Hope the pics help show what I've described. I can e-mail larger pics if you wish, I didn't want to take up too much space!
Good luck! 
LMD