Any recommendations are appreciated. We will only have one day for either.
Loredana Caserta for sure! I think you will find several references for her on this forum.
For Pompeii, my recommendation is Dr. Anna Maria Esposito, who goes by “Pina.” If you have time that day for Pompeii, she might also be able to fit in Herculaneum, which she did for us.
I posted about her last year, and she has also received rave reviews from others on this Travel Forum. Here was mine:
https://community.ricksteves.com/travel-forum/trip-reports/don-t-go-to-pompeii-or-herculaneum-without-pina