I took an underground tour that was just so-so. Afterward I realized that there were two possibilities, more or less across the street from each other, and I'd mistakenly gone to the one with that didn't have great reviews. Sorry, I can't find the names.
Consider Ischia instead of Capri.
I had such a great lunch at Antica Trattoria da Carmine that I went back a second time, recommended to me by dear departed Zoe. Locals eat there, limited menu, homey atmosphere, cheap (even by Naples standards) and in the heart of the old town on the main street - via dei Tribunali 330. I was there in February too - they weren't open every day inspite of what their website said, but there was a sign in the window with current hours.
For pizza, the RS book says: the two most famous pizzerie are Antica Pizzeria da Michele (corner of Via Pietro Colletta and Via Cesare Sersale) and "the less exceptional" Pizzeria Trianon just a few doors down, at Via Pietro Colletta 42. I went to da Michele and the line was really long, so I went across the street to Trianon, and was underwhelmed. I got to da Michele a day or two later before the dinner crowd (in Naples they eat earlier than most of Italy) and the pizza was definitely good. There are 2 choices (marinara or marherita), no wine, bottled beer, water, coke and Fanta orange. Service is fast (and they're impatient if you can't decide) - their profits come from turnover. They are really crowded at lunch time too.
Near your B&B is the Church of Santa Chiara - don't miss the cloisters.
Pompeii - I thought it worthwhile to walk out to the Villa dei Misteri for the in situ murals (most of the artworks are in the Naples Museum). I skipped the walk to the amphitheatre on advice from friends (we've all been to better ones).
Crossing the street is more difficult in Naples than Rome. Cross with others. It's often safer to cross in the middle of the street than at corners (motorcycles ignore traffic laws completely, most drivers seem to consider them a suggestion at best). Plan to walk or use the metro, street traffic is usually miserable.
Last thought - 3 days isn't enough!! As Harold likes to say: the only subtle thing about Naples is its charm. I hope you and your family find it.