If you have children, then that is probably the most impactful. They will need/want the same living standards as other people. They get the full package of other impactful things you mention plus some more like house building. For example a young family does no longer live in the same small 2 person flat, but instead builds a house (or lets build). Especially in first world countries and developing to first world countries, where everyone wants to have the high living standard, having children will be the most impactful action.
Perhaps there should be a high CO2 tax on having children, which one needs to continue to pay, while the children live?
Perhaps there should be a high CO2 tax on having children, which one needs to continue to pay, while the children live?