The OP does seem to be overthinking things when it comes to school ski trips in the future. I think we all understand having a need for financial security. But I'm curious just how much of this is new and how much was discussed previously between you and your DP.
You say you are in your 40s. How long have you been together? Since your 20s? Or just a couple years? Did you actually HAVE long term plans? If so, when did you make them and have you discussed them recently?
Honestly, I would have thought this kind of thing would have been something you discussed once you realised you were pregnant with the baby you now have. How long has he been working this job? Surely you must have had some idea of his ideal career path when you got married?
Has it changed drastically?
A mortgage isn't the end all/be all in life. We've owned a home twice in the past, but currently rent (sold homes due to job moves) as it suits our finances better. As we are in our 40s, we are most likely not going to purchase another home, but we are not really worried about it. Lots of people live in flats with children - sure a big house with a lovely garden is nice, but not necessarily a requirement. It generally also comes with a hefty payment.
I wanted to be a SAHM and couldn't for years. Now I am a SAHM mainly because our DS2 is disabled and I am his main carer. DH works, but doesn't have very high pay. I could earn more if I was working, due to the nature of my previous work, but DH cannot cope FT with DS2 and therefore I am home. It's not necessarily what we planned, but sometimes you have to adjust your plans to reality. I would never put pressure on DH to be making more money - he feels enough pressure as it is, and the last thing he needs is that. We make do with what we have, and that's life.
I think, based simply on what the OP has said so far, that the title of this thread is horrible, in the sense that she feels he is not living up to her expectations and has let her down. He's working, they have somewhere decent (I assume, as she hasn't drip-fed anything about that) to live, and apparently enough money to cover their current expenses. Sorry, but lots of people are struggling with much worse situations. Couldn't you see it from what may be his POV? Would he be able to post on here "AIBU - I'm working hard at my job, trying to support my family, and my wife doesn't feel it's good enough - she still wants more?"