Well, I'll go against the grain. I ABSOLUTELY would. ...and I have threatened to do so. Fortunately, the threat was taken seriously, but it was made just the same. My issue wasn't the same as yours. We had a homework issue, and a talking in class issue. (2 separate children) The 1st had developed a bad habit of not doing her homework. She was told, in no uncertain terms, that if there were any more missing assignments, that she would be staying home. She did her homework. The 2nd, we kept getting notes and calls that she was "disrupting the class" by talking and socializing with her friends. Again, the threat went out, one more complaint from the teacher and you will stay home. Guess what? No more complaints.
If your child does not have some sort of disability or delay that causes behavior problems, then, yes, I would use this as "goal." If your trip is close, I would tell her "if you hit again, you will not go to WDW," and remind her daily, "remember if you hit someone today, you will not go to WDW." If your trip is far away I would do some kind of chart or "hit jar" type thing where a mark is made or a marble is put in the jar for each offense and when it is full, the trip is off. A 7 year old without delays or disabilities is old enough to understand "no hitting." I might also work some kind of reward into it like telling her that if she reaches her goal of no hitting, as a reward for working so hard she can plan a whole day. Pick a park, and restaurants. Or go to BBB or something like that.
While I think it would be a very hard lesson to learn, it may be the thing to catch a child's attention. I don't really understand why a child should have the same privileges as the rest if that child is not behaving and the rest are.