In the Versilia waters lives a big school of dolphins (bottlenose dolphins). The area is part of a protected reserve known as the Pelagos Sanctuary, that comes from an international agreement between Italy, France and Principato Monaco promoting the safeguard of marine mammals. In addition, the Regional administration of Tuscany has created the Tuscan Observatory of Cetaceans.
In Viareggio you'll find an information centre and a permanent exhibition within the local Maritime Museum about the activities of the observatory. The info point is managed by the CeTuS association, which also arranges dolphin tours your kids might be very, very interested in.
The sighting tours happen aboard a catamaran (called “KRILL”) and are for a maximum of 8 people. Contact the CeTuS Association for more info, here's the link to the website.