It would make sense what you're saying and I could remember things wrong but as far as I remember, reading the books, all the kids in the series had only 2 birthdays so far.
For example I know that Sansa was 11 in the first book and was mentioned specifically being 13 in the latest books. As Alayne Littlefinger bumped her age up to 14 as to help her not raise too much suspicion about her real identity.
I remember Arya's oldest age being mentioned to be 11 in the latest books and she was 9 when it all started. Same with Jon. 14 when the books started, 16 now. Dany is one year younger than Jon so she cannot be much older than 15 in the books at present moment.
However, in the TV show she's supposed to be 17 when season 1 starts. Maybe someone got confused when they wrote down the info in the wiki?
Btw the books begin in 298 AC and the year we're at right now - and the year that will probably be the one where the war with the wights starts is 300 AC. So yeah... A Song of Ice and Fire is only 2 years of crazy shit happening. It might seem like a bit much when it comes to the things Dany manages to accomplish in the books, for it to only have taken place over 2 years, but I'm pretty sure it would line up if we got all the facts in front of us and pieced together that timeline ourselves
Read no further if you do not wanna hear a fan theory I subscribe to, that is related to the AC-timeline.
I think 300 AC will mark the end of the Aegon's Conquest timeline and a new one will be implemented after the war with the undead. Some people have talked about the dynasty being demolished along with the Iron Throne and democracy becoming the new ruling system in Westoros when the war ends - which would be some sweet, sweet irony for all the people betting on this or that character ending up on the Iron Throne in the end