@wilderint - only the children under the age of 17 count. (and I assume they all have Social security numbers and they were on your joint return)
there are press reports that there have been errors related to dependents.
it will get corrected, it's the timing that I suspect you won't like:
here is the worst case scenario:
The stimulus payments are really based on your 2020 tax return (income, dependents, etc).
The IRS is using either 2018 or 2019 – whatever is available - to ESTIMATE that payment
When you file next year there will be a “settle up” section on the tax return. If you are due more stimulus, you will receive it through the 2020 tax filing. If you received too much, by law, you are not required to return it
So technically if one of your children is 17 on December 31, 2020 it is unlikely they are eligible for the stimulus. But when you do your "settlement" if you received too much money, you won't be required to return it. Likewise if you had a child in 2020 and obviously that wasn't on your 2019 tax return, you'll get the $500 stimulus payment on the 2020 tax return next year.
hope that helps
