There’s been a lot of speculation on the Mombasa aspect. I suppose it’s possible that Daddy Obama had some reason to go to Mombasa - political party headquarters? maybe the university where he got an undergraduate degree? near the airport? It’s odd but not impossible.
There is the issue that Granny Obama says that she was present at his birth. She wouldn’t have been that old at the time (in her 40s, probably), so it wouldn’t have been impossible for her to get to Mombasa.
Why she’d go is another matter. Maybe Daddy Obama wanted her there, maybe he felt that he wanted it clear that Baby Obama was his and belonged to his clan, maybe she even intended to take the baby back to her village to be brought up there. Who knows?
They’re odd aspects, but don’t really make it impossible.
Resort town and port, newly part of Kenya, presumably would be the coolest location without AC for a pregnant woman in there in the summer. I can imagine various reasons why a first-timer to Kenya would be taken there.
We have all been assuming they travelled by air. If they went by ship then Mombasa would be the likely port of entry.
“Odd” pretty much sums up the whole saga of the Dunham’s/Obama’s. Nothing about any of them comes as a surprise anymore.