It's not a white lie - a white lie is telling someone that the outfit they are wearing doesn't make them look fat - it's harmless. Withholding money for services rendered is stealing. Why should someone get something for free, that they're not entitled to, when others in the same situation are paying money for the same thing?
That and even if they did say, "Oh, and your son turned 3 this year?", it's not like they are going to argue with you if you tell them it's wrong. Typos are just as common as lying about ages.
