I would also suggest a full day in Syracuse. Arenella beach (Spiaggia Arenella) , just south of Ortigia (the ancient Syracuse island site) is a great place and there are some organised “Lido” which you can check out. We were also based just north of Catania and went early morning to Syracuse, started the day on the beach at Lido Arenella, had a shower on the Lido, changed, and spent the the rest of the day from early afternoon on Ortigia, visiting the place, the stunning Cathedral (with visible structure from the earlier Greek Temple), and the many other sites. We had an afternoon snack and pistachios tart (that I still dream about) at Pasticceria Artale. For Dinner (needs to book well in advance) for a nice fish meal head to “La Medusa da Kamel”.