Indiana feather ~ Your ideas are good ones, but just make sure the grass isn't too long because it can cause an impacted crop. I do "yard work" with my flock everyday, and they love when I dig up some dirt where they can find grub worms and other delicacies. Since my chickens are pets, and I don't have a large flock--not a lot of beaks to feed, I give them a variety of treats: sunflower kernels (TSC apparently has tastier ones than RK), safflower seeds, freeze dried mealworms, chopped nuts, cut up grapes and cut up blueberries (whole can be choking hazard), and cut up salad greens (grass size). Yogurt is good for them-- I usually mix some seeds with it since they're not crazy about mushy things that cause them to wipe their beaks too much! They like bananas enough to put up with mushy mouth. haha Two favorites that I don't offer as much are Craisins and shredded mozzarella cheese. Mine never liked scratch grains/cracked corn. I don't give them our leftovers because I figure that the levels of salt or other seasoning is disproportionate for their size. They eat more healthfully than we do!
When it's cold outside, especially when it's miserable cold rainy weather, I make them scrambled eggs (their favorite) or oatmeal with raisins.