...well, if it arrives [insha Allah it does...the sooner the better!!

] ....it will just sit in his mailbox until he returns....but a few weeks after that, he should also be receiving the first letter from the NVC, which is the Choice of Agent letter....but they also send it to you...so if they're successful in getting it to you in Egypt [my husband hasn't received a single letter...haha] ...then it won't hold you up at all....but if he could, he should have a friend check his mail for him while he's away, so they can update you guys on that...
all the best