Any children born prior to the renunciation taking effect (and it can easily take months for it to become effective once applied for), will likely be citizens at birth. You may be able to renounce the citizenship of any existing children at the same time you renounce yours. You can ask the consular officer how it affects any currently unborn child.
Depending when the child is expected, you may consider beginning the renunciation for all family members after the child is iy”h born. (Assuming they advise you that you can’t renounce it for a yet unborn child at the same time you do so for yourself.) You can ask them how you can renounce the citizenship of your minor children.