Hi MaryDee
You will love Sorrento. I have been there years ago, but not with Just You. I can't really remember which month I went - think it was September and the weather was lovely. Do go to Capri and Pompeii if there is an opportunity to do so. Even if it is too hot in July, you will have a nice time. All coaches have air conditioning nowadays so you should be comfortable whilst travelling.
Have a wonderful holiday.
Jaya