Even if the humidity goes to 10% while you're gone it's really no big deal ... if he has a stuck shed when you get home just soak him to get it off.

Stuck sheds have no direct adverse effects on your snake at all. The biggest problem is eyecaps which might make feeding difficult and if you allow multiple stuck sheds to "build up" he could get skin legions.

There's really nothing to worry about. Enjoy your trip!

-adam