At that age those youngster's should be weened from their parents already so I would say to go ahead and treat the parents. Can the youngsters eat by themselves? I ween youngsters from 25-30 days old that's around the age yours are right now.
They are about 3 weeks old and are not walking around yet, but they are doing deep knee bends and are getting active. I noticed today some regurgitated seed on ones chin, so thier getting more than milk.
They are not even close to 3 weeks if they aren't walking around yet. Are they fully feathered? If you birds aren't walking around yet then they are still to young to be weened. Hold off on the mocidectin plus.
Ok I'll take your advice. It was time to worm and they are the last babies in the loft right now. I also suspect mites are about. I did a through cleaning and dusted the loft. I guess I should spray the group one at a time.