we went in june. umm....i would say definetely how you cant miss athens(all the historical stuff, the port, lots of cool museums, marketplaces) or santorni (beaches, sunset, glassblowing, partying). crete has really amazing fresh seafood and kinda like a little whole country. i didn't go to mykanos but i've read how its like santorini but more expensive. and i would definetley say if you are only planning on 10 days that you are gonna have to cut some things out of that itinerary. the other places i couldnt really say.

and santorini we had the best hostel in the world i think
everything looks exactly like the pictures and it was right in the center of town and crazy cheap too. i mean $20 per person a night, what a steal!!
the other places we stayed were just mainly cheap and close to everythign but i imagine you guys are gonna go for something nicer.

oh and here's the link to ferry schedueles