A small error in the personal data is not a problem. As long as the names are correct, and the error did not result in a ticket for the wrong age category.
So in your case you can just travel. Have a nice trip :-)
Note: Booking so far in advance you probably got a Saver Day Pass, right? Did you also get the Half Fare Card? When you buy that as a tourist you get the complimentary Family Card, which allows your children to travel for free.