If they want to undo a few more buttons that's fine.
The Sun (2011)
He was in a mismatched blue jacket and trousers and his top shirt button was undone .
The Sun (2015)
Personally, I don't like seeing men with their buttonsundone and their hairy chest showing.
Times, Sunday Times (2010)
Definition of 'button'
button
(bʌtən)Explore 'button' in the dictionary
countable noun
Buttons are small hard objects sewn on to shirts, coats, or other pieces of clothing. You fasten the clothing by pushing the buttons through holes called buttonholes.
Definition of 'undo'
undo
(ʌnduː)Explore 'undo' in the dictionary
verb
If you undo something that is closed, tied, or held together, or if you undo the thing holding it, you loosen or remove the thing holding it.