What a fantastic selection, no wonder you are having trouble. I have liked Boy in the striped pj's and My sisters keeper but both are a bit harrowing so perhaps not so good on hols. Equally Pillars is fabulous but if you don't get into it you are lugging a brick around!
On that basis, my favourite is Esme Lennox, with these close behind:
Thousand Splendid Suns
Dissolution
Tractors of the Ukranian
Nightwatch
Thirteenth Tale
The Observations (reminded me a bit of The Fingersmith if you've read that)
And have a fab holiday!!!