Forget Pompeii, Herculenium is ok but Pasteum (South of Naples) and Ostia Antica are the business. Believe it.
The cafe there is modest so a picnic lunch would be in order but not essential.Travel on the bus/train is 1 Euro each way and the entry fee of 6.50 Euros is more than reasonable.
Returned to repeat the best dinner experience at the Trattoria Palerro. Seems Mary is now on kissing terms with the owner.