I know another couple who went o/s together after being together for a couple of years (he left w for her) and that was the end of the R. They worked out then that they were both very different. Holidays are often times of tension if communication is not really good. So often people go with different expectations(-eg one wants to visit all the sites, the other is there to relax) and then the arguments start. I know that I've experienced both the wonderful, romantic holidays and the tense ones!
Their trip is what it is but you too have to be kind to yourself at this stage. Love you!