I actually had the same dilemma and posted this thread recently: http://www.dogforums.com/2-general-dog-forum/55677-vacation-board-hire-pet.html
I'd suggest boarding but spend some time trying to find a good boarding place--one that keeps the dogs in a location with a decent amount of space and lets them out at least 3 times a day. Ask other dog owners what places they use in your area. If your dog has never been boarded before, I think a "practice day" is a great idea before you go on a longer trip. Then your dog will see that this boarding is just a temporary thing. In my area, you can board your dog at a good place for $10 to 15 per day.