They will stay with the hen mum up to a point but then the issue with water will arise. You could keep them off water till they are feathered, then wean from mum and gradually get them onto water, shallow bowls initially.
Feed-wise they will need waterfowl crumb/pellet to give them the correct amount of protein. If you feed ordinary chick crumb they will develop angel wing, a deformity of the primary flight feathers caused by too much protein. The hen will be fine on this and if you wean them promptly at 6 weeks or whenever they are fully feathered then she can go back to her flock and a normal diet and ultimately come back into lay.