T.F.
It won't hurt you to enter. I wouldn't pay a high entry fee. The main thing places like that want is your contact info so that you can get bombarded with advertising geared toward your age and children's age group.
If you are interested in getting your children into modeling, do so at a legitimate site such as Kim Dawson or Campbell agency (just to name 2). I've been in the modeling industry all my life and my daughter models as well.
Don't go into it with high expectations. Keep in mind to never, ever spend money at an agency. If they want you...they will contact you and you will be paid for jobs you do.
Best of luck!