Shaving are ok,maybe just a little bit of hey for them to lay on?
I have tried hay for my ducks and yes, it is gross. I have also tried shaving and although they look nice as the start, they just get too messy too fast...For me I have used an old mat (yes I know it sounds weird) but it is a huge old carpet mat that I got at a garage sale and I can just pick it up and hose it when it gets too dirty. It is absorbent too! But yeah any bedding you use will get gross with that many duckies! hehe
I'm having very good luck with mulch. The kind you buy in bags for your garden. I first laid down some Stall Dry to help with absorbancy, then some DE, then a thick layer of mulch. I simply rake it over a couple of times a week and it doesn't smell and the ducks can still dig thru it.
I'd use something else, like patio stone, around the pool area though.
I use small rock...Very easy to hose off. Has not caused injury to their feet. Mine free range most of the day.
I also have sidewalk blocks for them to lay on and piece of rubber stall mat that I hose off.
No flies, mud, or stink....
Yeah, you pretty much have to try things and then see what actually works best for your set up. So far what I do has been working very well for me.I am planing on putting small rocks around their pool area.
The first picture I uploaded is a old picture.