Well I do have a secondary check, the code I have adds up all the age years returned from travellerages, then when they come to enter the traveller details they are given those (possibly incorrect) dates again. If they change them to the correct dates, and the years differ by more than 1 year from what they were quoted, they will get an error message saying go back and re-do the quote.
We also have a minimum age on the policy, at least one traveller has to be 18, so if all the dates were entered as rubbish (e.g. years would be 2022) then it would raise an error.
Its not ideal, but it does sort of work.
I will investigate your textbox option!