Turns out the small child that shouted "Fireworks!" was almost right - it was a single firework exploding. A firework show, as 'twere. It's all in yesterday's comments.
Still sounds like there may have been something of an accident, and I hope no one was injured badly - but it's nice to know what it was.
Thank you SeaLevel & Hinemoa for solving that mystery for me. Y'know, I think that may be good enough for me to forgive that little matter of Hinemoa owing me one kalua pig!
Which reminds me, I never got around to going to check out da plate lunch at either of the New York branches of L&L. Mmmm. 'Course my favorite plate-lunch place on Oahu is the one right next to the Aiea Snack Shop, which is my favorite manapua place. I will judge this mainland L&L franchise based on this standard: If, when I close my eyes & bite into the barbecue short ribs, I suddenly hear the creak of an old wooden screen door & the crowing of the roosters in the dusty little street that runs behind the odd little hexagonal Aiea Library, instead of taxi horns & sirens, then they've done a good job.
Now I've gone and made myself all homesick plus cut into my falling-in-the-water time tonight (there are things that I have to finish before I go tonight). Great use of time, there. Thhhbbt.