I doubt there's much to be learned from trying to fix a chronology to events, it was patently obvious in 2008 that the reason 'Dreams' has no chronology is so that the protagonists could not be followed. You'll learn more from the mistakes and omissions if you look for them - no lies are ever perfect, and they do make mistakes.
As for the record of airline arrivals in the period from July 1961 up to the end of June, 1962, one needs to remember that the younger brother Omar, who was introduced in 'Dreams' as the one who 'went away and got lost' attended a private high school in Boston CLASS OF 1966, and if that was a four year high school, he would have arrived in that period shown, which means he and the kenyan both arrived in Boston in the summer of 1962 and it is recorded, they shared accommodation.
170 Magazine Street, Cambridge.
Articles about Omar Obama, or Obama Onyango as he now calls himself, state his commencement as 1963, but I have my doubts...Class of 1966 commences in 1962 by my calculations.
It seems to make sense that the brothers would arrive in Boston at the same time, doesn't it?
...The only African student at the school, Obama stood out in a number of other respects. Not only was he three years older than most of the boys in the sophomore class, his arch colonial accent immediately marked him as different. That he initially lived with his brother in a rented apartment in Cambridge, a place often churning with visiting Kenyan students, added to his exoticism. But within a few weeks the normally reserved Obama had made a large number of close friends, many of whom remember his sunny disposition nearly half a century later...
Somewhere in my memory is the usage of “commencement” in conjunction with high school graduation, I.e. “commencement ceremony”, rather than usage having to do with “beginning” school.
Would this help the timeline; that article mentions omar being three years older than the rest of the classmates.
Snippet from your post for reference:
“....Articles about Omar Obama, or Obama Onyango as he now calls himself, state his commencement as 1963, but I have my doubts...Class of 1966 commences in 1962 by my calculations......”
If the commencement was in 1963, then he would have started in 1959, using the “commencement” to mean graduation.