I'm significantly older and with kids already but one thing that jumped out was your comment on your husband's career. I'm a consultant and it is pretty exhausting. I find combining it with family life difficult and I'm planning to take a step massively back (or off!) next year when my son starts pre-school. One thing that's struck me as I've got older is that while it is not easy to do consulting part time, there are sometimes ways - particularly if you are in your 30s or older with a bit of a network and track record behind you.
For example:
- I have a friend who was a consultant but took about 7 years not doing paid work after having her kids. Because she didn't need to work (and kept saying "no") she managed to accidentally negotiate a 3 day a week, only 1 of which was in the office, term time only contract.
- A FoF works for one of the Big 4 accountants (but in consultancy rather than accounting) and works 3 days a week term times only: "behind the scenes" (rather than client facing) but still at a senior level.
- Another friend got very into gym instruction and fed up with his Big 4 consulting job. Because he had the power to walk away he now does a mix of gym teaching, freelance work for his old employer (but without all the corporate b/s he used to have to deal with there), and some smaller projects that he does independently as a freelance with start ups (which is his top favourite thing). He doesn't have kids: just wanted a more fulfilling life and could afford to take a massive pay cut to do what he actually wants to do because he had always been frugal, got paid to go to the gym, paid of his mortgage early, etc. etc.
- A former colleague moved back to her home country when she had kids, but still does work for us on an ad hoc basis when we are super-busy (but only if she has time - so generally in term time - and when we are super-busy).
This is the amazing thing about being nearly FI even if you aren't fully FI: having the flexibility to be able to take the kind of work that won't pay regular bills but will contribute towards your retirement accounts or help pay for one-offs or holidays is actually incredibly valuable to lots of employers. If you have the right network there are opportunities out there.
Obviously I'm not saying your partner would be able to juggle one of these with a tiny baby, but once baby is a bit older and could go into part time nursery etc. then your partner may well find that if he maintains his network there are opportunities to do bits of top up consulting/freelancing or one-off projects that would help you to FI if you aren't fully there yet. It's one of the big advantages I've noticed to my friends who've had kids later rather than earlier, that they already have this network and so can find these opportunities (which are never advertised!) more easily. Obviously there are lots of advantages to having kids early too, but I think by mid 30s chances are your partner will have a pretty good network and if he keeps the lines of communication open then opportunities to e.g. help out when his old employer are completely under water on an "ad hoc" basis may well be around. So it doesn't necessarily have to be "all on you" to finish your earning if your partner stops to take care of babies.
In terms of expenses, if you are happy to take hand-me downs babies and young children cost very little beyond childcare. As they get older they tend to have more opinions about what they wear and we've started to have to do e.g. gifts for birthday parties, and pay entry for more museums, transport, etc (whereas babies and toddlers go free most places). My son at 2 is already having opinions in fact (much earlier than his sister! But he is happy to "shop" the hand-me down bags as he doesn't know there is another option yet!). My daughter is 5 and cares a bit more about what she wears, and we're offered fewer hand-me-downs for her these days - but she also wears her clothes for longer so it doesn't cost much. Holidays get more expensive if you fly, and also once you are constrained to school holidays, but not so much if you drive or take trains (and term time only becomes a consideration when they are a bit older).
I believe teenagers are much more expensive, but we're not there yet!