Great news, Caleb.
I, too, echo what has already been said about the backpack. Only four weeks after surgery, you still need to be quite careful if you want to minimize scarring and discomfort.
I suspect that you will be fine on the drive because the meds will make you sleepy and you'll still be woozy from the anesthesia. You might not be perfectly comfortable, but if it's only for a couple of hours, that's not so bad. I had an hour-long drive directly after my surgery--practically the minute I woke up--and I was in and out and didn't care about much of anything.
I was really glad to crawl into bed when I got home, though. Er, until I remembered that I would have to sleep on my back for several weeks. Definitely not a win.