So sorry that your home has been hit with this, and I sincerely hope you don't have any annoying and rude remarks on this thread, BB.
Sometimes doctors won't give tamiflu to kids - my doctor wouldn't when my son was in middle school. There is also a window of time in which they will give it - the faster you get in and get diagnosed, the more chance you can actually get tamiflu from the doctor. After that window passes, it won't work and they won't prescribe it.
Flu will kick your butt, truly. You may find that he starts to feel better in a few days and will want to get up and be active. Don't let him overdo. All of a sudden, he could crash. What he needs most is rest, liquids and food. (According to the doc when my husband caught the flu back in JUNE!) The way the doctor explained it to my husband, if you fight the flu by not resting enough, it will win.
I'd expect a full week out of school to be honest. Get some stuff from the teacher and let him work on it when he's feeling better.
Hope SO much that the rest of the family doesn't catch it.
Dawn