John -a
All is possible with a 54ft yacht, you should be able to average 7-8 knots under power , and around the same with a good breeze.
Distances invlved Athens to Kea 36 miles, about 5-6 hours and Kea to Mykonos 45-48 miles.
I am at a loss why you want to to go this island, Mykonos is the Gay captial of the Aegean, makes Key west and Pea town look tame, yes it is a party town and an expensive one at that too. The Marina/Harbor is miles from town, and basically a disaster, dirty and un finished, also you will have cruise ships lying right next to you with no stop, annocements of when the next trip in to town is or when the next meal time is......
There are so many more beautiful islands than mykonos, Kithonos is stunning with the beautiful little town of Loutra, and nice marina, go around the south side of kithonos to St. Stephanos bay and
anchor off beautiful village hamlet and enjoy true greek island hospitality.
The island of Serifos is breath taking with is beautiful bay/harbor and stunning town perched high above the harbor on the rocks and cliffs that surround this natural harbor.
Paros is great very cosmopolitian and much more fun than Mykonos, plus you will not be ripped off for a beer or iced coffee.
Naxos is a must to see, this island has so much to offer, and now with a brand new marina in town, with YES>>>>>POWER,WATER AND EVEN SHOWERS ON THE DOCK, it going to be a hot spot to see and difficult to leave when you have such great facilities there....
My advice skip Mykonos, and if your crew really want to see it send thme on a day trip via ferry while you hang out on a better island...
Weather patterns this time of year have been wierd, lots of days with no wind and then some days of moderate to brezey conditions, Meltemi has not arrived yet and could be a late player, may be starting mid to late july, then again it just may not show up at all....
Good luck and have fun