The audio post worked great for me. And I can relate to your observations as well. I also get grumpy at the start of a vacation. If fact, when I have to leave my office to go on a vacation, I experience great sadness and withdrawal rather than joyous anticipation.
I think it is because my work life is where almost everything comes naturally to me with little effort. I am almost always "in the zone" and very happy. There's order and control. I feel great. Work is my spiritual practice.
When I'm on vacation with my family I really have to "go with the flow" and "let go". Much is out of order and there's a lot out of my control. The change hits me hard and it takes me awhile to tap into a spirit of adventure. But I do get into the swing of it after a day or two. And I'm sure you will too.
(However, I'd be lying if I didn't admit that the best part of vacation for me has always been coming home. :D)