Received stimulus based on 2018 dependents but 2019 changed, what now?

I received my stimulus deposit for myself, wife, and grandchild i claimed as a dependent in 2018.

 

NOW, I'm doing my taxes, and my son's, and my grandson will be claimed by my son, as well as my new granddaughter who arrived in 2019.

 

So based on online-turbotax calculator, my son should receive 500 for each child. 

But they already sent me the $500 for one grandkid.

He will file taxes this week, as will I.

 

What happens now?

What do I / he need to do in order to get the $500 for the new granddaughter?

Will I need to give back the $500 for grandson, and will IRS pay him for the grandson?

 

Please advise.