I'm in a somewhat similar situation myself because my DH currently has 8 weeks of vacation he has to use by next year while I have 2 to 3 weeks. If he decided to go someplace on vacation without me where I wanted to go, yeah, I'd probably feel a little jealous that I was stuck at work while he got to go have fun. However, I'd have no problem if he wanted to go someplace that he's really excited about and I'm not as eager to go to. Heck, I've encouraged him to go visit his family with some of this time (not that I don't want to visit them, just know that he's got more vacation and wants to spend time up there). I don't think separate vacations are necessarily the harbingers of doom that some seem to view them as. I'm an only child, and I like being alone occasionally. In fact, when my DH went away for a week on a business trip, I was really afraid I would be lonely and would miss him. As it turns out, I enjoyed having the time to myself and was just starting to miss him around the time he was scheduled to come home (good timing, right?
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However, I can't help but think I've watched the Dr. Phil show one too many times, because the following quote keeps running through my head: "Do you want to be right, or do you want to be happy?" You say you'd discussed this before you got married and she was okay with it. To turn around now and say she's not okay with it doesn't seem fair. However, fair may not be what's important here. It's probably more important that you come to a mutual agreement that will make you both happy. Maybe instead of going for the whole week, you fly down Monday evening and fly back on Thursday. Then you're only gone when she's at work anyway and she might enjoy having some time to herself in the evenings. Or go from Wednesday to Tuesday the next week, and she can join you on the weekend.
Before we were married, I told her this was something that I simply didn't want to give up, and she said she understood. So, I'm planning on going in February by myself, and then we're going in July the 2 of us.
She's a bit upset about me going away for a week by myself, and I'm feeling guilty about it.
BTW, I also think the proper resolution depends on how she's handling the "being upset" about it. If she's openly said, "hey, I know we talked about this and I said I wouldn't have a problem with this, but now that it's really happening I realize it does bother me for blah, blah, blah reason" then I think she's being mature about it and you should respect her feelings. If she's doing the female pouty thing and saying she's okay with it when you can tell that she's not, then that's a different story and more worth discussing then the vacation itself.
Hope this helps some - good luck in whatever you decide!
Alas, he preferred to spend a week in Myrtle Beach with our friends then go to WDW. 
