Part of it also for hollyrachyx is the uncertainty and probably a little trepidation in leaving something familiar behind as this isn't just a holiday for her and her partner.
I do remember the feeling a little. On one hand there's the excitement of going somewhere new and the start of a new life as well as the challenge and on the other, leaving the safety net of what you've become used to and are comfortable with.
At least they will be going to be with family (on one side anyway) who will be able to show them the ropes of living overseas.
We've never looked back and have thoroughly enjoyed our time since we left UK in March 2004.
All I can say to you is enjoy your new life and take each day as it comes. Be aware that foreign bureaucracy can be a right royal pain in the backside - just smile, say please and thank you, never lose your temper but be forceful when necessary and you will get through it.