You don't have to break your backs, or the edges of your kiddy pools, by lifting them to dump out the water. Not only are you going to damage your body and/or the plastic, it also makes the whole area around the pool turn into a bog.
Instead, take a hose and siphon out the water so it flows far away and preferably into a hungry garden bed. It will work as long as the end of the hose is lower than the bottom of the pool. Stretch out the hose where you want it, place one end into the duck water. Holding it under the surface, take another hose and get water flowing into the siphon and out its other end. Once you get the water flowing, remove the fresh-water hose and keep the siphon hose in the pool. You may have to hold it down on the bottom with a brick.
Another way to empty a pool is to attatch a bulkhead fitting to the bottom edge of the pool. You cut a hole in the pool and screw this fitting into it, then you can attatch a faucet & a hose fitting on the outside. And then attatch a hose to it and drain the pool through it. Again, it works if the end of the hose is lower than the bottom of the pool.
I try to empty my ducks' pools every 2-3 days, give the bottom a swipe with a brush to get most of the crud out, and refill. Every few months I'll try to empty them out, let them dry & air out in the sun, maybe even spray some clorine bleach on the bottom. Then rinse, refill with water, & let the birds refill them with poop...