I'd feed them before you leave - perhaps when you get up for your very early flight. See if they'll go again when you get to the airport -- they may very well surprise you, because other dogs have been there before them, they may want to leave their mark too
I went thru this at Christmas time. I didn't have as big a gap in flying time as you, I choice to not feed them before getting on the plane in the early am and planned to feed them once we landed, but ended up waiting about an hr longer until we got to my parents house -- I think all the excitement and unusual activities kept their minds off food, because they never once barked, acted hunger, etc.
Good luck with your flight. Have a great time in a much warmer environment
