Inheritance methods for non-techsavy family members without a third party.

Hi. i am seeking for a proper chain of inheritance to my wife and kids which are both not tech savy and kids are too young. I know about Casa but i am not sure if a third party is the best way to go.

Is there any option that is guaranteed my kids inherit the keys if me and my wife pass away unexpectedly?

Handing the seed to a lawer that takes care of inheritance feels not good enough tbh.

What options do i have?