Remember a lot of the previous comments are about maternity leave taken before you got SMP for 9 months.
I had 5 months off with DD. At the time you got 6 month's SMP. When I worked out how little money, after nursery fees, train fares, lunches etc, I took home for the first month over and above the SMP I would have got it was really depressing!
This time I am not going back to work until 9 months. Would that be a better option for you - to use up all the SMP period, then a month of holiday if you want to take it to 10 months? You don't mention any company maternity pay so assuming you just get SMP.
DD settled into nursery really well at 4 months old. DS is getting a bit clingy and I am concerned it will be harder for him.
As you are the main breadwinner is it an option for your DP to take some additional paternity leave?
Any chance of working at home one day? Even if your baby is in nursery all day, you won't have to commute and will see them morning and evening that day?
Working 12 hour days will be really tough. I do pick ups as I have a much shorter commute than DH so I always had to leave the office at 5 to get to nursery on time. This meant I was much more focussed and didn't faff about as I knew everything had to get done within a certain time. I did go in early and rarely had a lunch break. There were occasions I would be dealing with matters on the train, or in the evening after putting DD to bed. Are you able to speak to your boss about the workload. Are you able to tell your employer that you want to pick up from nursery two days a week so, say on tue and thu you need to leave at x time?
Agree that now is not the best time to think about it. Wait until your baby is a few months old and rethink.