Better if you don't treat parents that are feeding babies. Unless a baby
actually has canker
, then better off to not treat and let him build up immunity. If a baby does come down with canker, then he would have to be treated. The amount an adult bird would get would be too much for a baby, so you would have to probably take over the feeding of the babies so that they didn't get too much med from the parents. Or maybe by treating the parents individually and at night, so that they wouldn't be feeding the babies for hours, you could do that. But doing a flock treatment in the water wouldn't work as the babies would get too much of the drug.
In that situation I would use 50mg per adult bird each, one time daily for 10 days. I would treat individually by tablet. It would be easier to break up a 250 mg tablet than a 500 mg tablet. You can quarter a 250mg tablet and get 62.5 mg which would be fine.