Your and your children are visiting during a season when it may be raining a lot in the mountains. I would definitely steer clear of mountain hikes, as they can be dangerous if you are unfamiliar and it is raining.

There is plenty of hiking near the coast. For example, if you go to the Turtle Bay Resort, there are some nice hikes in the forests adjacent to the beaches both north and south of the hotel. The hike to Makapuu lighthouse is a nice one, and on a nice day, you will have great views. Have you hiked up Diamond Head? Or, if the tide is right, hiking from Beach Road at the base of Diamond Head toward the Kahala Hotel. Turn around at the Kahala Beach Park. Just make sure that the tide will allow you to complete your walk.

There are plenty of tourists boats available at Kewalo Basin. There is also an Atlantis submarine tour.

Have fun!