September weather, honestly
Late September sits near the peak of Central Pacific hurricane season, which runs June through November. Direct hits are genuinely rare — Iniki in 1992 was the last major one, and Lane in 2018 was a near miss that mostly meant rain.
The realistic risk isn't disaster, it's a few grey days and a cancelled boat trip. Refundable lodging plus travel insurance costs maybe $200 of the $1,500 we'd save.
The upside nobody mentions: the ocean is at its warmest, and the North Shore is still calm — the big winter surf that makes snorkeling impossible up there doesn't arrive until November. It's arguably the best snorkeling of the year. We'd miss whales entirely.
The school week
North Carolina has compulsory attendance, but Wake County has a process for requesting an excused absence for educational travel — submitted ahead, at the principal's discretion. Worth a call to the office rather than just having her out.
Teachers are usually accommodating in fourth grade with a week of advance work.
And it's worth saying plainly: a volcano, a coral reef and Pearl Harbor are not a worse week than the one she'd have in a classroom.