In Prince Caspian, the children are just a bit, perhaps a year, older than when TLTWatW left off. I remember the children were going back to school, and sitting on a bench when they were pulled into Narnia again.

In The Voyage of the Dawn Treader, Edmund and Lucy go back with their cousin Eustace. So my impression was the Edmundand Lucy were still rather young..Early teens to preteens?

In the Horse and His boy, the Children were young adults. I think I remember Susan being of marriagable age, so I always got the impression that she was older, and that Lucy was a young adult, certainly at least an older teenager.

It's been many years since I read the books, though, I could be wrong.

K