I'm hoping to get the Buttons to a point where opening the cage frequently won't bother them, but we'll see
I love that cage and want a few myself. lol...
Well...
Quaillady beat me to the safe list. lol.. I had to leave for last min. shopping.
I have mint and Rosemary in my walk in Aviary, but no birds yet, so I don't know how bad they may nibble. Another thing you could do is shallow dishes or bird seed grass. Just plant a simple finch seed mix and it will grow like grass.
ETA: Plant several a few days apart and you can just rotate them.
Replying so I will remember that list for later. It's awesome! Are there any kinds of grasses they shouldn't be around? I have Coturnix, not Buttons, but I'd imagine they're relatively the same, right?
Lavender works as a calming plant. You can grow it and dry or use an oil to keep your quail calm. I find the dry herb better because you can just sprinkle it around the cage. If you use the oil you can make a spray it or defuse it.