What would be the classifier for children? I used con, but it wasn't accepted. Would người be correct?
Đứa is already a classifier in this case. Trẻ means young person in this case. Con would pair with nít (kid) although you can also pair both as đứa con nít.
I see, thank you. So is it also possible (in another context) to say một đứa trẻ?
Yes that would specifically mean "a child".