She could have easily had Jr in Canada, remember Canada is also a member of the Commonwealth and B.C. did have socialized medicine at the time, it was in effect by the late 1950’s. It would make more sense for her to have Jr in Canada than in Kenya, especially given the ease with which people traversed the border back then! She was familiar with the area as well.
Especially since she visited a friend in Seattle shortly after his birth and didn’t even know how to change his diaper.