Wow !
Just make sure you have Nothing in your hand luggage or pockets that could possibly be construed as a weapon.
Bear in mind you guys will go through security at every airport.
No matter what you've read, there is NO acceptable size knife you can take onboard an international flight.
My top flight tip.
Take an empty water bottle in your hand luggage and fill it from a water fountain or Tap after you've gone through security.
It'll save you an absolute fortune in buying water.
Personally I wouldn't take a sling through either, I know a lot of the guys do.
And I've had them in my hand luggage in the past.
But you guys are going through a bunch of different security points and it only takes one arsehole with a hangover to remove it/them from your bag.
You have no rights, they can and will take anything they deem a 'threat'.
If you just assume all airport security personnel are complete arseholes, you weren't go far wrong