In reply to JamButty:
Your entrance ticket to the scavi at Pompeii, ridiculously cheap, also gets you into Herculaneum, the villa at Oplontis, the museum at Boscoreale (my son and I found the walk there from the station "interesting" but it is worth it when you get there if you are nerdy) and the villas at Stabia (my son and I found the task of finding the right bus just a bit too interesting and gave up and went to have lunch at the seaside instead but I am sure they are excellent if you can find them).
Any trip that does not involve walking down a street in Naples is going to be good.
Vesuvius is wonderful - you get a bus ride most of the way up and then a pleasant walk to the top. And then you realise why Sorrento is lovely and the rest of the bay of Naples is a dump: Sorrento is outside the volcano zone. Everyone else will, one day, get 15 days' notice of an eruption and will have to leave. Not a place to invest in property.