If you tell the kids they're going on a trip, they will want to know where. And then they will ask you everyday is it time to go yet. And if they should start packing? And what will they do there? And is it time to go yet? And what they should bring? And what they will eat and see there? And is it time to go yet?
If you just wake your kids up, say "get dressed and grab your toothbrush" they will be a bit confused for a while. They'll get ready and get in the car, all too bewildered before they can ask "where are we going?"
When the kids were younger, we packed them up into the car in the dark of the early morning and drove to the airport. We were landing in Orlando before they were awake enough to wonder what was going on. I loved the sight of their eyes getting big as we approached the gigantic Mickey Mouse and Disney signs and they realized where we were. Since then, we haven't bothered to tell them where we're going unless it's a long enough trip that we need them to pitch in and pack up their own stuff (or last year, there was this process of picture taking and going to a government office for passports, that gave away our plans). Otherwise, we just give them instructions of what to do on the way to the car - bring your bathing suit, get a water bottle, bring a book for the car-ride.
This year, we gave them a few days notice, now that they're old enough to start making plans with their friends and had a pile of library books to return. (Things were so much easier when they were little.) But there were still the "ooh's" and "aah's" and "how is the water so blue?!" as we made our arrival on the small island nation. And so began another family vacation - a week of 100% family time, new adventures, and new surprises. And new memories.