In the larger towns on Elba, such as Portoferraio, Marina di Campo, and Cavo, there are lots of hotels and cottages available for rent. Restaurants are everywhere, along with tourist shops and gelaterias. (Lots will be closed if you go in the off-season.) ~~~~ You can go swimming, snorkeling, or boating, plus there are cheesy touristy things like miniature golf and vineyards. Out in the countryside, there are beautiful views and small, picturesque villages like Rio Nell'Elba. ~~~~ Basically, Elba is a great weekend retreat if you want to get away from the hustle and bustle of Florence for a few days.
There are several ferry companies that will get you to and from the island, several times per day. Count on spending about $40 for two bodies and a car each way.