Hello,
You and your son have chosen some wonderful places to visit. I have been to each of them with my daughter (although on 3 separate trips), so yes, memories will be made! :)
I do have one idea, if you haven't already made, or can change, your flight between Rome and Athens. It will mean skipping Pompeii, but adding many other memorable sights. And most importantly, it will be easier!
Visit Florence as planned. Eliminate Naples and either visit Pompeii as a day trip OR visit Ostia Antica. So, add 1 day to Rome and 1 day to Greece. Fly to Athens and take a 4 Day/3 night Classical Tour with C.H.A.T. tours. Finish your trip with any remaining days in Athens. Fly home.
So, something like this:
Florence - 3 nights
Rome - 4 nights
Greece - 8 nights, with 3 of them on the tour
Advantages to this itinerary:
Pompeii will be very hot and crowded in June, but Ostia Antica is an easy 1/2 day visit, just 30 minutes from Rome. Take a look at City Wonders tour for Ostia Antica. We just took this tour in October and highly recommend it. https://citywonders.com/rome-tours/ostia-antica-tour-from-rome
You will have the afternoon and evening to either fly to Athens or enjoy more Rome sights.
The CHAT tour will take you to Meteora and Delphi but will also include Olympia, Corinth Canal, Epidaurus and Mycenae. If your son loves Greek Mythology, he won't want to miss these. The advantage to the tour is they do all the driving! It is a BIG Loop, but you will be able to sit back and enjoy the scenery between stops and it is a very affordable tour.
https://chat-tours.com/tour/4-days-classical-tour-tour-9/
With the added night in Greece and the 3 day tour instead of your original plan, you will probably have time for a day trip out to Cape Sounion and the Temple of Poseidon.
I am happy to answer any questions. Whatever you decide, I am sure you will have a wonderful time. Enjoy!