chartering a sailboat (with captain)

I can’t comment on sailing in the Cyclades, but a number of years ago we sailed twice with The Moorings in the Caribbean. We sailed the Grenadines and the BVI’s. We had a Captain & a cook. We enjoyed both sailings very much. Exceeded our expectations. I believe they sail in Greece. moorings.com

The best advice on boat charters is NOT to start in Pireaus, but fly to an island like Naxos or Paros & start there ... otherwise takes too long to get to Cyclades. I planned a very successful trip for my neighbor & her brother, that started on Paros. I can give you the information but it would require a week's charter and I think you would have a LOT of trouble booking a captained sailboat for just 3-4 days. A fallback might be to stay on one island -- Naxos is good for this -- and book a captained boat for 3 or 4 one-day trips... You can do full & long days & come back at sunset... going to Antiparos, & the 3 small islands just south of Naxos. There are 3-day cruises there too... but I think on a luxury yacht sleeping 6 or 8 .. very pricey.

Thank you Janis and Janet! Appreciate both your answers. I found that some of the local Greek charters listed on the various sites I found were a lot less than the large international companies like Moorings (which looks fabulous!). And Janet, I did find several that offer shorter sails, and yes, leaving from Paros, but was hoping that folks on the forum might have firsthand experience. (And I'm happy to share the websites I found, but can't recommend anything at this point, since I haven't used any of them!). We are four "adults" (two parents and two young adult children who will not want to share a double berth!) so a boat that sleeps 6+ is actually good for us.)
Anyway, the thought of several long day sails from Paros is interesting and also worth a thought...many thanks. I'm sure I'll have dozens more questions as I get into the planning, though I've already learned a ton from earlier posts!

Here's the link to the charter my neighbors loved: http://www.archipelclub.com/en/yacht-charter-greece/beneteau-50.php If their bookings are low, they might go for a 4-night charter; I doubt just 3.

Thanks Janet! I did come across that company, and they do actually offer a shorter cruise in the shoulder seasons: https://www.archipelclub.com/en/catamaran-charter-greece/short-cruises.php
But it is a fair bit pricier than some of the other options I've seen, so again, trying to understand my choices. This is one of the others (that is well reviewed on TA) that offers shorter cruises, and is similar in price, so maybe I should assume this is a good benchmark https://www.sailboatchartergreece.com

We went though a British company - Cosmos Yachting. We sailed Croatia but they have boats everywhere. Also check out Greece Travel.com Matt Barrett. Hope that helps

Here is a different suggestion from a local (Greek).
First, noway you can start from Athens/Piraeus and just for 3-4 days. Like someone else comment ed u need to fly to one of the Cycladic islands and start from there. The next best thing is to start from Portoheli which is located 2 hours away from Athens in the Peloponnese; best area of Greece. You will be exploring the best part of Greece to get there, like Corinth, Mycenae, Epidaurus and beautiful Nafplio.
These people are not the big names you see if you Google what you are looking for. Whe in Greece you should be looking at small boutique agencies and not the big faceless travel companies, still always researching them before proceeding.
The only have one motor boat with 3 ensuite bedrooms. They'll be happy to do as many days as you like but not Cyclades. Instead you are looking at places like Hydra and Spetses islands, Monemvasia, Elafonisos island, etc. Very unique, off the beaten path, amazing beauty, an experience you'll be suggesting to other people. Greece is not Mykonos and Santorini... Let me know if you need more help.