If your child has an SSN, they are eligible for the $2000 child tax credit instead of the $500 credit for "other dependent." Also, for 2020 only, a child with an SSN is eligible for a recovery rebate of up to $1100.
If your children are eligible for SSNs, don't file until you get them. You can't amend later to claim the extra money after you get the SSNs, the law blocks that. You must have the SSNs when you file an "on time" tax return. A return can be "on time" if you file as late as October 15, as long as you filed the form 4868 automatic extension before April 15. If your children are eligible for SSNs, you will need to file the extension form and then apply for their SSNs, and wait until you get them.
