Turtle Beach on Maui is a fun place to take kids. AKA Ho'okipa Beach Park. There are always at least 20-30 there, but sometimes it's in the hundreds. Naturalists are often there to answer questions. It may not be a paid job but they are very good at answering kids' queries on the lives of sea turtles.
Great place to watch some crazy good surfers too. The waves in winter are impressive.
We occasionally see monk seals from Hono Koa, but the best view of monk seals is during fishing season from the high-rises, when one of the big fishing operations sets their gigantic net to catch fish. This particular time, a single monk seal gets in the action by jumping in and out of the net, stealing fish. It was fun to watch two years ago from our friends' 14th? floor at Kahana Beach. Maybe it's the 12th floor. That was spectacular. We spent hours watching them with the nets, pulling them up into large boats that were loaded with ice.