Kelly, I've got a set of the walmart dry bags, but hadn't seen the stuff sacks. PU or silicone doesn't matter so much. Price/basic functionality trumps weight in this situation. I'll go try to hunt some down.
JP Those are great links on the silnylon. Easily some of the best prices I've seen.
This is my first time to gear up a group and it amazes me how quickly the little things add up!
I've even thought about using just a mesh bags for the kid's clothes, since large ones can be had for cheap and could function as a wash bag, mosquito headnet, etc. $3 mesh bags: