Child modelling is not so easy as people think it is.
A successful career for a child model depends on whether the parents have the available time and are willing to make the commitment to take on the responsibilities that come with the job.
First of all, it's important to realize that there is a wide demand for all types of kids as models. So that means any child who looks great in photographs might have a career opportunity.
Try to get the good pictures of your kids.
Just submit your kids pictures in various agencies and wait.
A genuine agency will never ask you for money -- never.
A genuine agency will never sell you modeling classes.
A genuine agency will never sell you photos -- never pay the agency for photos, pay the photographer directly.
Beware of agencies that direct you to a specific photographer. They are probably getting a commission.