Such a mission is probably on top of the Maslow's hierarchy [1]. Starting first by making sure you can sustain your family seems more natural to me!
Now I know that people went broke and miserable and also changed the world, but being happy feels like a achievement, too :-)
[1] https://en.wikipedia.org/wiki/Maslow's_hierarchy_of_needs
Maslow's hierarchy was never supposed to be a prescriptive account of how we ought to live.
I don't take the hierarchy as prescriptive either, I just noticed that it matched, mostly, my baby steps to change the world.
If so, then I don't think so. I am running a bootstrapped startup (https://www.wisecashhq.com) and sustaining my family right now (and I expect, 99.9% sure, that the startup will make a better future for them, as well).
This just requires picking a model where you can sustain your startup and your family, there's no need to dichotimize between both here.
I didn't understand what you mean with "it doesn't account for planning into the future"? I do believe that securing resources, health and property does account for planning into the future, actually.