I think portable blackout blinds are one of the best inventions of the past few years. The first time we went on holiday, our eldest was up until past 10 each night because his room was bright and he was frightened of missing anything. Next time we went away, we took blackout blinds and managed to pretty much keep him in the same routine he has at home.
In fact, they made bedtime so much less stressful, that we use blackout curtains at home now too. There's a rather fabulous pink sparkly pair on
Nappy Valley at the moment.