first job is to talk through the scenarios - not a happy conversation but a necessary one. These are:
both of you die before the kids are independent: you need to nominate guardians or people to choose guardians.
one of you dies before the kids are independent: different effects depending on who it is. You are just as important because without you, he will struggle to pay for all the things you do.
one of you dies before the other (which of course will almost certainly happen) but after the kids are independent. Where does the other one live? How does the mortgage get paid?
both of you die (which is of course a definite).
also: he loses his job (quite likely for anyone, so get working on those savings) or gets too ill to work. Or you get too ill to be childcarer.
given these unhappy situations, what would be the effects? How much money would be needed in each situation to keep things going? Where do you want possessions (including the house) to go?
and also (I'm afraid) if you split up - what happens to you?
once you've got initial ideas, you can look at life insurance quotes (to pay off the mortgage and to provide the childcare) . You can then also get will and guardianship set up.
but the first thing is to decide what you want to happen in each circumstance.
may you both live to a healthy old age; but as parents, you must plan for the worst case.