Drink lots of fluids, chicken noodle soup, tea, whatever you have to do to get those fluids in. Even if you have to give you son lots of Ginger ale, 7-up, mountain dew, whatever...if it gets him drinking, do it.
Give the antibiotics 48 hours. Usually, people start to feel better after 2 days of meds. They should start to feel better before you go. And if they need a break in the afternoon, give them a break. They may still feel a little yucky, but a mid-afternoon break should make a difference.