usually European strikes are announced in advance. I don't think the circumvensia strikes very often? Here is my prior DIY post. I have more disboards posts on almost all the ports, if you search. There was a thread from a few years back with lots of great info, called Med planning (?)
DIY to Pompeii by train. super cheap and you can decide at the last minute whether you are up for Herculaneum. For kids/teens, definitely Pompeii--they have/will study it in school and it is an important ruin to see. It was #1 place to see on our trip to Europe. For easy DIY--1st, right off the boat, stop in a tourist souvenir shop at the port and look for the cardboard book that has the overlay of Pompeii as it used to look (they also have them for Coliseum). These books are also at the airport. Then walk to the end of the port (pedestrian friendly), cross the small street and buy a ticket from the tobacco stand to/from Pompeii and good for all trams (5 or 8 euros PP), then take tram #1 right there to the circumvensia train station--5 minutes away. Get on the next train to Sorrento (one every 30 minutes). Get off at Pompeii Scavi (means excavation) and walk to front gate--right around the corner and buy your tickets--kids under 18 are free. With that little book, there is no need for a tour--get a map and go to the sites that interest you (or even better, download Rick Steves tours for free). My tweens/teens loved looking at the book and then at the ruins. It is hot and they lasted for 2.5 hours.
There is a café/gelato place inside Pompeii that you can cool down in, plus a few nice café style places right outside the gate where we got slushi drinks. Get back on the train (cross under the station--the train goes the opposite way back). The great thing is, you can decide on the fly if you want to get off at Herculaneum or head straight back for the ship. With DH and I alone, we did both. The next trip with the kids, we went to the ship--they had had enough---and it was a great day. remember to get off at the circumvensia station and get the #1 back--not the main trenitalia statin. We made that mistake--no worries, just hop on the train back 1 stop--15 minute detour to get the next train. It's pretty foul-proof to DIY. This is about the easiest port to DIY and with kids free At Pompeii and Herculaneum, you can save a lot of $$. We felt 100% safe at the port, on the tram, circumvensia train and at Pompeii. have fun! It's a great place. Elaine (ps. when we went in 2013, they also had a 20 euro PP bus to Pompeii at the end of the port, but we wanted the train to be able to stay as long or short as we wanted).