To see Elba in all its forms, I recommend renting a boat and exploring the different coves that the island offers ... if this is not possible I recommend an outing with the Baiarda (sea baptisms, diving, trips with guide), it's worth it.
https://www.baiardaexcursions.it/
For the little ones you cannot miss the exit with the Natilus that will allow you to see the bottom without getting wet.