Jeff
Planning to land at Nikumaroro on the reef flat would have been pretty risky, tides, terrain, and all that. Without a good survey, they wouldn't have known much about what was there.
Interesting thought to use Nikumaroro as at least an initial target that can be seen from a longer distance than Howland, and then navigate to Howland as your destination, but I think Fred was confident enough in his celestial nav to take the straight shot at Howland. Perhaps too confident as we now know.
Andrew