if your qualifying dependent was on the original return then your advance payments should not be delayed. the IRS just started sending them out so it may be a few days before you receive yours. if the QD wasn't on the return it may be 6 months before the amended return will be processed
the IRS will have a portal to update dependent info in late summer (sometime after the third week in August)
https://www.irs.gov/credits-deductions/child-tax-credit-update-portal
