Mentioned by Hawaii Travel with Kids
Top 6 Free Things to Do on Oahu
"Ho’omaluhia Botanical Garden is a 400 acre protected area that was originally built up as flood protection. It offers events like camping, drawing or painting classes, and specific catch-and-release fishing days on the weekends!. The garden is about 35 minutes from Waikiki (by car or service only) on the eastern side of the island."