I'd even argue that it's oversensitive to call those drawings "racist caricatures". To a certain extent, it just seems to be Hanks' poor grasp of faces (compare the "Send men and provisions!" guy).
Furthermore, I think it's fair to consider that in a society more segregated than ours, even a sincere attempt by a white artist to portray black people realistically would tend to emphasize the unfamiliar features, such as thicker lips.
To assume that white people are the norm and therefore depict other ethnicities as defined by their differences from the default is (or at least should be) outmoded today, but this kind of ethnocentrism isn't really by itself racist.
And as for the paternalism (maternalism?) of the story, consider that it was written at the height of the colonial era, with all of Africa (give or take) in the hands of European colonies, and native people hopelessly outgunned. So this village's inability to resist heavily armed gangsters doesn't necessarily show them as "children to be cared for" (they seem to have been doing fine up to this point, and they certainly manage to seize the opportunity for escape).
I feel like I've been spending way too much time defending a crazy person. It certainly wouldn't surprise me if Hanks was a virulent racist. I just don't see particular evidence of it in this story.