currently, it is expected that teh actual credit will be calculated based on 2020. (you and a child under 17 it's worth a maximum of $1700) against that the advance will be subtracted. if the credit is more than the advance you'll either increase your refund or reduce the amount owed. should the advnce be in excess of the calculated amount, it appears that you will not have to refund the excess or pick it up as income. based on 2018 your advance will probably be $1,200. if you file 2019 quickly enough you'll get the extra $500 for the child. so the question is do you owe more than $500 for 2019. if so I would delay filing also if you currently don't have the money to pay the balance.
be aware of state filings if your state has an income tax. many states have not yet extended the due date.
