Why do you need to plan for your family separately from him and only by knowing the exact amount he earns though OP? Can't you have the following sorts of conversations?
"The patio is on it's last legs and needs replacing, do you think I should get that organised?"
"DS1 is in Year 2, are we keeping him at St Hilda's or do you think we should think about moving him onto the prep?"
Are you happy in this house, we're bursting at the seams, as DS1 is due a school move, do you think we should think about moving to?"
There all conversations we had (well not the moving one). In the early days DH would sometimes say - x still owes me y - can you wait until I know it's in before phoning Mr Patio.
What I'm having difficulty reconciling is your desperate need to know so you can actively plan to spend and change your life and I wonder if that's what your dh is a bit shy of.
I'd also say that 15 years or so ago, with small children, we were a bit like ships in the night and I had sole responsibiity for children and home and except for knowing that we were comfortable and had enough and then more than enough I didn't know exactly what was coming in. I do now though (broadly - not to the last penny) but because I had no doubts in him, for us it worked out OP and I have seen a lot of people with workaholic husbands fall by the wayside. My tastes and spending haven't really changed over the last 25 years and I wouldn't spend any more now than I would have 20 years ago because there is no need to do so.
There was a time when I found out that DH had salted away a six figure sum whilst still watching the pennies (him), but I thought it was funny and went and had plantation shutters fitted to the front of the house (my money) "without consultation". I would say we have no secrets but I don't know exactly how much he has (although I know where all the policies are and where the list of assets is) and he doesn't know exactly what I've got either but likewise he knows where the file is. However, I would be extremely cross if he opened my bank statement or payslips and he'd be cross if I opened his post because it would cross a personal boundary and for us would indicate a lack of mutual respect and trust.