That would be too tight for me, especially considering the fact that you simply can’t say for sure beforehand how much you will be working with children.
With the relatively (!!!) low income and completed family planning, you could take the risk, preferably with a fixed-price contract, to keep costs under control. Then it’s a matter of sampling everything in advance, insisting on the presentation of all possible extra charges, and still planning enough buffer. And not fooling yourself with statements like “we’ll do that later bit by bit,” “from the current salary,” “we save here and there with a lot of DIY” – that won’t work with your income.
On the topic of children: almost all the mothers I know started working again later than planned (because there was no daycare place, because they didn’t want to leave their child so early, or because it simply didn’t work out) AND later reduced their hours again because 25/30/35 hours were too much. Because they wanted or had to be more there for their children!
In our case it was like this: I also started working later than I had thought before. 20 hours worked well, now the children are 6 and 4 and I work 30-35 hours, sometimes 40, and that’s already a lot and only works with some support and a cleaning lady. Or with a husband who only works 37 hours. Dancing, gymnastics, soccer, early intervention... you have to manage all that too.
At the beginning of family planning, we couldn’t have afforded a house. Only 2.5 years ago could we start planning. In the meantime, we both changed employers, I increased my hours (not for financial reasons, but because the job requires it) and our income is almost 30% higher. That makes sleeping much more relaxed – even when a vacation is possible despite new construction.
So again: I would let some time pass and then decide. For us it was perfect that way. By the way, we are 36+40.