If you don't see any of them sampling the water by morning you can show them where it is again by gently dipping just the tip of their beak into the water. As soon as you see one of them drink you should be set. Chicks love to copycat. As soon as they see one doing something the rest should...
Yeah, they CAN go for up to 3 days with the yolk sustaining them. But so far mine have all been eating and drinking heartily by no later than the end of the second day. I have seen where people do leave them in there for 2-3 days. But for myself, I prefer to leave them no more than 24 hours...