Fun!! I leave mañana!! So excited!!
No way on this planet would I update my iOS before a trip. Nothing to do with app compatibility concerns, but I think they are valid, everything to do with Apple updates. Too many times new bugs are found after an update, vacation is not where I want to discover updating my phone cut its battery life in half because there's a bug in the update! (NOT saying there is but it has certainly happened before.) Therefore the update waits until I'm back from my trip!
ETA: sure enough there are apparently tons of complaints that iOS 11 is killing battery life...
http://bgr.com/2017/09/20/ios-11-features-iphone-7-6s-battery-drain/