I think being among the very last people to exit MK, holding hands, maybe pausing by the castle for a gentle kiss, and telling her how much she means to you would be a romantic moment.
There are lots of ways to be romantic without spending a fortune (which is also fine if you can afford to do that, too!).
Calling ahead and having a special dessert made for your anniversary dinner.
Are you buying a special gift for her?
If you gave a little more detail about your trip (where you're staying, where dinner will be on your anniversary, which park you plan on visiting that day, etc) you would probably get alot more ideas specifically suited to your details!
BTW, I think the fact that you are even planning a romantic trip is fantastic. The fact that you are asking for suggestions is wonderful. Happy Anniversary.