Greece itinerary

Couple of comments.

1. I would go to Athens only once at the end.
2. You can't ferry to Chania but Heraklion. They are several hours apart.
3. You are going to spend a lot of time in transit for 3 nights on an island. I would consider going to only two islands.

I agree to much moving for just short stays at each island.

Pick two islands Paros & Santorini and save Crete for another time.

OR

Go to Crete for your entire stay as there's more than enough there to keep you occupied without losing time traveling from one island to another.

Most travelers recommend saving Athens for the end of your trip to ensure enough time to get to the airport for your return home.

Good sound advice from Beth and tommy. You only have 12 nights so you have to plan your logistics carefully. Every island hop uses up half a day by ferry. The ferry to Crete (Heraklion) basically uses up a full day as the ferries on that run are returning from their morning trips. That means the earliest you can be in Crete is between 5 and 7:30 in the evening. And you still have a 3 hour bus trip to get to Chania.

So you will have to prioritize what you really want to see and drop something else.
Here are my thoughts.

Arrive Athens, you need 2 hours to make a connecting flight to Chania. Spend 7 nights in Chania. There is so much to do in the Chania area. Be sure to get a hotel inside the city walls in the old town and Venetian era harbour. A week in West Crete will go by fast.
Chania 2022. https://www.flickr.com/photos/stanbr54/albums/72177720299646015
Western Crete https://www.flickr.com/photos/stanbr54/albums/72157632115757899

When you leave get to Herakllion in time for the morning ferry to Santorini. The KTEL bus should be timed to get you there before the ferries depart. If you are risk adverse then spend that last day in Heraklion and overnight there. There are several hotels in Central Heraklion that are within walking distance of the ferry port.

Ferry to Santorini. If you take the first ferry departing you will be there before noon. Santorini will be crowded and expensive but it is worth it. It lives up to all the hype. Three nights in Santorini is all my budget can stand.

So 10 nights, now I would fly back to Athens which will give you 2 nights there. That is a bit rushed 3 nights would be better so you could drop 1 night in Crete or 1 in Santorini.

As already stated experienced travellers often recommend you get to your first island the day you arrive in Greece and leave Athens to the end. There is little point in visiting Athens twice on a visit just to it once.

Ok---taking everyone's comments into account so now thinking Paros 4 nights with a day trip, Naxos 3 nights, Santorini 4 nights, fly to Athens for 2 nights. Crete for another time.

That works better.
A good day trip from Paros is the excursion to Delos and Mykonos. Delos was a major religious centre that was destroyed by Pirates. The site is very good. The excursion continues to Mykonos. This gives you the opportunity to experience Mykonos without having to pay exorbitant Mykonos prices.
Day trip to Delos and Mykonos https://www.flickr.com/photos/stanbr54/albums/72157637922138466
You will love Naxos it has a lovely waterfront promenade an old town topped by a Venetian era Kastro . Some great beaches and mountain villages.

With as little time as you have I would not spend 4 nights in Santorini. I would take a night and add it to Athens unless you have little interest in it (two nights gives you only one full day). The other possibility is Naxos. We had three nights in Santorini and four in Naxos and wished we had another night in Naxos. (We had 3 for Athens which seemed about right).