Traveling with Family

Looks like you have done your homework that seems like a pretty good plan. Just a few comments.

On day 3-4 on the way to Nafplio you might want to stop at Corinth. You can see the canal and possibly Ancient Corinth and Ancient Nemia. It was a sister to Olympia and had its own games. The stadium is still there. The kids will love having a race from the starting line. Both sites will take about an hour. If i had to choose one it would be Nemia.
Here is what you can expect in Nafplio and surrounding area.
Nafplio and Peloponnese http://www.flickr.com/photos/stanbr54/sets/72157632094108982/

You will love Chania. Its a 14th century Medieval city with amazing back alleys and Venerian harbour where you can step back into time. We always stay in the old town back alleys. The town beach is about a 15 minute stroll to the west of the city walls. The area of Theotokopoulou street is full of hotels in every price range.

If the beach is a must for you then you can look to the west at Agia Marina where there is a whole string of hotels.
Chania http://www.flickr.com/photos/stanbr54/sets/72157632117917828/
Theotokopoulou St area http://www.flickr.com/photos/stanbr54/sets/72157632118491316/

Elafonissi is quite nice but if it were me I might be tempted to take the day excursion boat to Gramovossa and Balos lagoon. You get two great beaches and a pirate fortress on that excursion.
Gramovossa, Balos and Elafonissi https://www.flickr.com/photos/stanbr54/albums/72157698932695812

Day 10 is going to be fairly long as Imbros is south of Rethymnon and it might be better done when you pan to go to Heraklion. Perhaps spend a night in Rethymnon on the way to Heraklion.
Rethymnon https://www.flickr.com/photos/stanbr54/sets/72157654700502270

Day 12 might be better logistically if you combine Rethymnon with Imbros and perhaps Meladoni cave.

Ancient Aptera, Melidoni Cave and village. https://www.flickr.com/photos/stanbr54/albums/72157672118379637

I noticed that you had Nafplio and Tolo listed for days 3-4. We were in this area in early June and it was hot! We would go site seeing in the morning and then hit a beach in the afternoon. We visited all three beaches in this area.

But Tolo was the only disappointment in our two week trip to Greece. Rick Steve's book touts it as the best beach in the area but it is not very well kept. The sand is nice but we found the changing rooms to not have doors, there were no public bathrooms, some trash in the water and beach, and chair rentals to be more expensive than we expected.

We much preferred the town beach in Nafplio which is rocky but well kept. We brought water shoes in anticipation which you do need. There is a restaurant there which is more expensive than others in Nafplio but still reasonable and provides a great view which we enjoyed.

Our favorite beach was Karathona. You can walk there from the parking lot of Arvanitia beach and it is a beautiful walk. It is also only partly shaded and got very hot. Half of our party walked and half drove and we reversed going back. It is about a two mile walk along the water. My husband and his brother walked back and they thought the sea front walk was among the most beautiful they had done in Greece. (I walked there and the heat did detract from my enjoyment). It is sandier than Arvantitia (town beach) but not as sandy as Tolo. But it is clean and not crowded (in June) with a beach front tavern with good prices, bathrooms, and inexpensive chair rentals.

Skip Tolo!