I called DME, yesterday, with a similar question. They told me to cross through what was wrong and write the correction right on the tag. Plus, they corrected the information in their computer while I was on the phone.
Our error was a little more serious, though. We have 14 people traveling on two different airlines out of two different cities. One of our female travelers was mistakenly given the last name of one of the other families. I was concerned that the resort might not be able to pull up her room info unless it was corrected. DME assured me, though, that hand-printing the correction right on the tag would work.
I'm sure they're right.
Pat
23 days and counting . . . again!