I'm more conservative with chicks the first week or two.
If the weather is good and a suitable temperature for them, I've had them outside for brief periods as early as one week old. They spend more time outside as they get older.
I don't give chicks anything but starter or starter/grower the first week. I just want to get them stabilized, after everything they've been through. This is with shipped chicks. When I do start giving them other foods, it's only a small amount, very finely ground and they get clean sand lightly sprinkled in a small container, so they don't over eat the sand. Sometimes it's hard to find chick grit. I grind up things like hulled sunflower seed.
For wheat grass, I usually just snip it really tiny for chicks, with a scissors. I take some blades of wheat grass, barely move the scissors and snip again. It looks pulverized or pulpy, rather than like pieces of grass. For larger chickens, I give larger segments, but not whole leaf blades. When they're eating growing grass, they can just eat what they bite off. I only grow wheat grass and sprout alfalfa for adult chickens in the winter, when the outdoor forage is under snow. The rest of the year they forage on their own.
