The important thing with grass and other plants is that drought will make them toxic. You have to have a watering plan to deal with that.
Also, you won't actually have a nice level lawn for very long. Chickens will dig and make ankle breaking holes all over the place, and they will uproot the grass, and defoliate any plant that tastes good. I ended up having to fence off sections of the yard and rotate the girls through those...the problem with that is It leaves them locked away from their nest box, which is affixed in their run. If I had known how attached they get to that box, I would have trained them to a portable box that could go with them, and made it lighter, with legs, and more rain proof.
I made the chicken sections around the edges of the back yard, leaving myself a small area of lawn to enjoy, where I could walk without stepping in a hole or chicken poo!
The areas each have shrubs for shade and hiding. Areca plam is not toxic, and it makes a lovely hiding place. There are varieties of hibiscus that are nontoxic. Hawiian Thai (pronouned tee) is very pretty and non toxic. It will grow back from the roots if damaged in a freeze, or it can be kept in a pot as a house plant that you can take out for the warm months. I have one mulberry tree in a pot to keep it from causing root problems, and a weeping mulberry out in the ground, because it is a smaller growing variety. The leaves are not toxic, and the fruit fall will be a bonus for them. Loquat is another tree that you can keep trimmed low, though it will try to grow large if you let it get away from you. The leaves and fruit are both fine.
The list of bad plants is really long, so it would be better if you identify what you have and research them.
I bought portable fence and posts and that was a mistake because it is too short. I clipped their flight feathers, but my clever little escape artist will find any gap between the fence and the ground to slip out and go wreak destruction. I wish now that I had invested in a better fencing product.
Good old sweet potato (not the ornamental type) makes a lovely spreading vine with edible leaves, and the bonus of free sweet potatoes for your family. Collards are attractive and have edible leaves. The leaves also grow large enough to create shade. If you put them into pots, you can move them around so the chcikens won't comletely defoliate them. My collards and sweet potatoes survived through frost and temps down in the low 30's.
Leaf fall is awesome because bugs and worms are attracted to the habitat the leaves make. I never rake away my dead leaves, but keep them in shady spots and the chickens love to go forage there. Again, having rotating areas for the chickens is nice because it allows the insect population to recover for a free source of protein. Also, the chickens help break down the leaves and fertilize via poo.
I hope this gave you some food for thought and chickens!
