
The run space depends on how many chickens you decide to have. If you do let your chickens out, though, they most likely will tear up your garden and take dust baths in it. You can try putting a chickenwire fence around your garden and clipping your chicken's wings. They also eat grass, but it grows back green and lush in the spring due to their... ahem... "droppings".

I think that the best bet for your yard is to let them run around on the grass or stay in the run. Yes, chickens can be trained to stay off things. I've almost trained mine to stay off the patio by tossing them back onto the grass or patting their fluffy little butts ("spanking") whenever they go on the patio. And it works!
And about the grapes... chickens love grapes. So you will want to put netting around the vineyard or else the chickens will eat every one they can reach.