assume they are going to use your 2019 filing if that is available. otherwise, they use 2018.
the $500 credit will only go to you for children under the age of 17 that were on your tax return.
for the 18 year old, if he filed his own taxes and was not a dependent on yours, he gets the $1200 as well.
if he was a dependent on YOUR tax return and filed his own return (doesn't appear to be your case, but wanted to state it in any event), he does not get the $1200 and you don't get the $500
