Well, my best advise for you would be to fence off everything you don't want them to get into. I have beautiful hybiscus plants and now they have little fences around them. My strawberries have a little fence, my garden has a little fence, lol everything I like has a little fence around. It only takes about a foot of fence to keep them out. Mine don't climb or try to fly over the fences. I just have to make sure they are sturdy enough to keep them from pushing the fence over. My fences are actualy the decorative white arch fencing that is only about 18 inches high. My garden is a three foot high fence just because I have an old lab that loves to dig in the soft dirt after we plant. As for the grass I just water regularly. They will LOVE to play and dabble in any water puddles that they get and they love to eat the roots off of the grass along with the grass. It would be a lot easier to keep the grass if you already have grass established before you let them loose in it. I think they just might eat new grass before it has time to grow and become strong. Just remember not to use fertalizers or anything like that it could harm the ducks. I have nice grass around my pond and they just pick at it but they have alot of other greens to eat. I spray they yard down once a day I think the grass really loves there poo.