Birthdates I'm making up trying to stay canon.

Molly 2/25/00

Dominique 12/15/01

Lucy 4/25/02

Louis 7/2/03

James S 10/15/04

Fred 1/26/05

Scorpius 12/26/05

Albus S 7/6/06

Rose 8/31/06

Hugo 6/29/08

Lily L 8/29/08

Roxanne 11/6/11