What is the best bedding for baby ducks?

I called my local tractor supply store to see what they use for their baby ducks and it is pine shavings. I've read so much online saying they'll eat it and die. Is this true? I'm trying to raise 4 2 week old mallards inside until able to be released. Whats the best bedding I can use that is both absorbent and cost effective. Right now they're in two large totes with paper towels in one for resting dry and none in the other which contains food and water feeders. A tunnel connects the two but they will our grow this set up probably in one week. So now whats a good idea to finish raising them inside???? I clean the cage 3 times a day now with hot sprayed water in tub....but how will the next cage be best cleaned out and the clean bedding added????