Most "eggsperts" will tell you the eggs are okay up to a week after laying, as long as storage is good (50-60 deg F) and they are gently rocked, not totally turned a couple of times a day. I've seen the recommendation of putting the eggs in a carton or secure container, on their sides, and just set one edge of the container/box/tray on a book or prop of some sort so the whole thing is tilted a bit, then tilt it the other way later in the day, back again the next day. Look up threads on egg storage and you'll get some expert advice. Over the weekend should be fine as long and the eggs aren't moved a lot, I think, just to let the air cell form and so they can recover from the trip.
Oh, you don't really know when those shipped eggs were laid, so assume they were 2-3 days old when they left, add shipping time, so a couple of days will put you right at a week or so. You should be fine.
I hatched chicks for school, too, but didn't plan it well and set them on a weekend. The kids did miss the hatch, but were a part of the candling and embryology. I brought the chicks in for them to see once they were healthy and stable, so it wasn't the end of the world, but it is good to plan better than I did! It was my first attempt at hatching so I did a lot of things very, very wrong. Good you are preparing yourself. BYC is an incredible way to learn, too!
