Alex’s friend Harmony took us on the amazing Wai Koa loop trail in Kauai. 2-2.5 hr walk, waterfall at the end, gorgeous, almost entirely flat. Highly recommended — one of the more beautiful, relaxing walks in my life, and I think kids would love it too. If you wanted, you could pack a picnic to enjoy when you reach the dam / waterfall, before walking back.
It can be a little muddy, so plan shoes accordingly.
https://www.alltrails.com/trail/hawaii/kaua-i–2/wai-koa-loop-trail
