Is there a way to block my ssn and 2 of my kids ssn from being used on a tax return?

No. Unfortunately not. If someone tries to claim your children before you file, your return will be rejected. If you file first theirs will be rejected. 

If your return is rejected you will have to paper file your return and prove that they are your qualifying child.

 A qualifying child is defined below as:

1. Must be a son, daughter, stepchild, foster child, brother, sister, stepbrother, stepsister, or a descendant of any of these, such as the taxpayer’s grandchild, niece, or nephew.
2. Must have lived with the taxpayer for more than half of the year
3. Must be under age 19 if not enrolled in school full time or under age 24 if enrolled
4. The child could NOT have provided more than half of their own support

Below is a link to more information that will explain the process to you if someone claims your child. 

https://ttlc.intuit.com/questions/3987334-how-do-i-dispute-someone-else-claiming-my-dependent