We went up Etna in 2015. It was pretty quiet at the time. You can go up to 10000 feet via bus, then cable car, then by massive 4x4 special vehicles. There's a touristy bit at about 5000 feet that isn't too bad. Above 10000 feet you have to hire a guide and be properly equipped. But the 10000 feet bit is good. You can stroll around the edges of craters and see the restlessness nearer the summit pretty well, though you're not actually looking at the main summit craters. It's a damn big mountain is Etna. If you go before June the top is pretty snowy.

Vesuvius is worth climbing, though it's a big tourist trap, and, to be honest, there's very little going on up top at the moment. The top few hundred feet is on foot and it's a slog through loose cinders. A really good place to go near there is the Solfatara crater at Pozzuoli (in the Phlegrean Fields, Campi Flegrei, a supervolcano that's left a huge caldera, mostly under the sea now, allegedly still an extreme danger. It was at the centre of the Campanian Ignimbrite super-eruption that may have seen off the Neanderthals once and for all). You may already know about Pozzuoli and it's bradyseism. It's a workaday sort of town but it's been the scene of some dramatic earth movements in the recent past. Take the Metropolitana railway from Naples to Pozzuoli and walk up the hill to the crater. There's no hill to climb to get into it. Boiling mud and very scary fumaroles, and the scene of a violent phreatic eruption in the 11th century. And it's where St Gennaro was martyred. I've seen his bones in a large urn in the Duomo crypt in Naples. Bloody Catholics have such good taste! There seem to be piles of saints' bones in many an Italian church!