Well I a have all my private key and passwords in my excel file and it is saved inside my usb. If something happens to me they will just open that usb and so they can access to my crypto accounts. But the main problem is not with the private key and password but it is because they dont understand how to use it since they are not interested and because my wallet has no bitcoins left because I always withdraw it to purchase the need of my family.
LOl, it is better that you just still keep your private key safe because one day, you will still have sufficient amount of money to store into it for future, but this excuse you gave will really not help you from getting bashed in future when your children open your wallet and found that you have not bitcoin in your wallet, they will not want to take that excuse that you were spending it on family need because they will never understand as much as you do understand yourself.
No matter how tight the situation may be, I think that it is best if you still have some bitcoin in your account saved for the future and never touch it no matter what. You just have to learn to be disciplined so that your children can have something to praise you for in the future when they need you the most to stand by themselves or when you die and they need something to continue with life.