Sailing in Cyclades from Alimos is doable, I would prefer to have 2 weeks time, but who wouldn't?? In any case the suggestion listed below is based on the assumption that (again) you arrive in Athens late in the afternoon so I consider Saturday a day you will not depart.
Sunday: Alimos - Kithnos (48 sailing miles)
Assuming that the wind is blowing from the north Kithnos is a very attractive place in terms of crystal clear waters and friendly environment for sailing yachts visiting the area. You can have a swim in Kolona bay where a part of land separates the 2 sides of the sea and will reward the hours of sailing you did to get there. In terms of mooring you have 2 choices, either to anchor in Mericha port which is a 10 min sailing distance from where you are located or to sail for approx 40 minutes and get to Loutra which is considered to be a nicer and more traditional environment.
Monday: Kithnos - Serifos (25 sailing miles)
Serifos is a quite nice island. She has the 2nd highest city in the Greek islands. On your way to Livadi which is the main port you can have a swim in the bays located in the east side and are protected from the north winds. The scenery can be magical and surely you will be happy with these quick swim stops. In the evening you can anchor in Livadi. Our suggestion is to take the bus or a taxi and visit the main city, while having a walk all the way to the church located in the edge of the highest cliff would be appealing.
Tuesday: Serifos - Milos (29 sailing miles)
Milos is a magical place in terms of the color of the water and the color of the rocks as well. You definitely need to go on the south side to have a swim and if you enjoy spending the night in isolated bays then MILOS is the place to do that. Two words characterize the scenery and this would be 'astonishing beauty'. The port is Adamas which is protected and beautiful as well
Wednesday: Milos - Sifnos (23 sailing miles)
Sifnos is our favorite island.. Not specifically for a specific reason, it is the atmosphere of this island that has something which makes you feel like home.. You have 2 choices in terms of anchoring. The first would be Vathi bay which is located on the south side of the island is a beautiful big bay that is a very protected shelter when the 'Meltemi' is blowing. You enter from a rather narrow entrance and suddenly a huge bay opens in front of you. Check it out, we believe it is worth sailing to Vathi. On the other hand Kamares is the main port of Sifnos. Not so protected from the north winds, but yet very friendly as far as the facilities and people ready to help you. Lastly we want to mention that if you are on the other side of the island (south-east) a new marina is available in Platis Gialos with all the facilities of a marina rather than a port. Don't forget to take the bus or taxi to visit Apollonia which is the heart of Sifnos in the evening..
Thursday: Sifnos - Kea (44 sailing miles)
Kea is the first island of the Cyclades close to the mainland. While returning from Sifnos, a nice bay for you to anchor is Vourkari. Not something fancy but it has nice waters and a restaurant or a beach bar for you to spend some time. The main port is Vourkari where you will find most of the Tavernas, Bars and restaurants ready to welcome our sailing friends.
Friday: Kea - Alimos (40 sailing miles)
Sailinf to Alimos from Kea is an easy trip as long as the wind is not in very high level blowing from the north. You can make a swim stop in Sounion so you can get the most out of the day before returning to Alimos. Be cautious with the riffs located outside Elliniko and Glyfada, keep your eyes in your maps and plotters and try to stay away from the coast on your way back.
Saturday: Disembarkation 09:00