My daughter (21) and son (17) will be traveling in Italy and Greece this summer and would like to know the least expensive way to get from Pompeii to Athens without losing a whole day.(night travel?) They also want to visit at least Mykonos and Crete while they are there...and again, night travel so as not to lose days. Is Crete their best choice, or would there be other islands that would be better..they plan on being in Greece for 6-7 days. Want to visit Delphi as well while in Athens.
Any help or ideas would be great.

Unfortunately the ferries require an overnight trip to Patras or Igoumenitsa coupled with a bus to Athens or Piraeus, so there will be some time lost taking the 'cheaper' option. Aegean Airlines has cheap flights to Athens from Rome and Milan. That might be their best option. Check with Alitalia as well.

Maybe if they can turn their Italian trip around and end up in the north (I know, it's counterintuitive on the way to Greece, but...) they can fly fairly cheaply with easyjet from MXP the ATH, but they'd better hurry and book...

WK

I've received two replies which were
very helpful, still looking for more.
Thanks!

I can't really add much to the great advice you've already gotten. Unfortunately, there aren't many options other than ferries and very limited flights between Italy and Greece. As far as I know, ALITALIA and AEGEAN are the only two airlines to fly between the two countries, and only from Rome or Milan, as already mentioned above.

I forgot to add that from researching our upcoming trip to Greece, I found that there is an overnight ferry from the port in Athens to Crete, which gets in around 5 AM.

EasyJet flies from Milan to Athens as has already been mentioned. You may need to start accepting the fact that the viable options have already been suggested and now you have to make some decisions.