I think that A should be done first in order to help the child breathe easier. This means that profuse bleeding from the nose and mouth should first be lessened. Since the child is already weak and is tachycardic, which means that the heart is beating faster than usual, there is a need to provide lactated ringers.
This will help correct the tachycardia and the hypotension that the child is going through. After doing this, all of the other processes should be done to ensure that the child will become stable. Adenotonsillectomy is a type of procedure that is done not only to remove the tonsils but also to remove the adenoids.