That is the problem with the whole CO2 footprint. You chosing not to fly is reducing your CO2 footprint, but airline companies will respond with ad campaigns and cries for state help and then other people will take your seat. But if you think it from a CO2 footprint perspective, you are responsible for CO2 produced by your actions. You take the decision to take that long-distance flight to Bali and that adds to your lifetime CO2 emissions. You put solar on your roof and that reduces your lifetime CO2 emissions considerably. And yes, an additional human on this planet will produce a lot of CO2 in his lifetime. And you as a couple are deciding to put him onto this planet - so from that perspective it is totally a good way to reduce your direct CO2 impact by deciding to birth another human.