Hi Julie
Welcome to the JY Community!
I'm not going with you this time but did the Pompeii tour in September 2015. You will have a super trip! If you put 'Pompeii' into the search function on the top right of the page, you will find loads of reviews, hints and tips other JYers like myself who have been before.
Two small tips that probably aren't in your joining instructions - take a bathing costume because there is a hot tub on the roof terrace of the hotel and, half way down the main street between the hotel and the ruins, you will find a paradise called 'De Vivo Pasticceria'. Just trust me and try it......
Happy to help if you have any questions
All the best
Mandy