Are all the Initiators/Cursed Children 10 years old? Were there none born after that?
According to the Black Bullet Wiki, the births of the Cursed Children are listed as a single year - 2021 - with Enju and Satomi pairing up in 2030.

So I guess the answer is yes, they're all 10 years old +/- 11 months.

The Initiator page also claims that they're all 10 year-old girls.