We've been going through this decision making process, as well. All of your points are good, there was just one I wanted to follow up on.
>I think that's a better use of my money than taking care of one human being.
I don't think this is necessarily true. Your child(ren) (and their child(ren) and their's, etc.) also have the potential to earn and donate money to effective causes. Those donations might end up greater than the ones you can accomplish in your own lifetime.
Of course, "net good to current and future humanity" is only one part of the equation.
I'm more altruistic than average. Regression to the mean says my kids will be less altruistic. And it would be rude to manipulate them into doing anything. I would surely do my best to instill the values I think are good, but in the end, it would be their individual choice.
>I think that's a better use of my money than taking care of one human being.
I don't think this is necessarily true. Your child(ren) (and their child(ren) and their's, etc.) also have the potential to earn and donate money to effective causes. Those donations might end up greater than the ones you can accomplish in your own lifetime.
Of course, "net good to current and future humanity" is only one part of the equation.