Meteora

Well, you can’t see the rest of Greece in 7 days. We went to Nafplio and Athens for our week which we really enjoyed. (4 nights Nafplio, 3 nights Athens). Meteora is fabulous according to people who have been but you have to decide what you want to see most because you can’t see it all in one trip.

Perhaps you could give us some idea of what your plan is so we can also add thoughts on the island hopping portion of your trip.

Meteora is about a 5 hour drive from Athens so that's 10 hours round trip and as already noted you will likely need at least a full day and two nights.
We actually stayed in the little village of Kastraki which is nestled at the foot of the mountains. When we got up the next morning we discovered we could see three of the Monasteries from our hotel. Pretty cool.

My advice is to time your arrival about an hour before sunset. Drive up to the Monasteries and get the feel of the location. At this time there will be hardly anyone up there so get all the photos you can because next day there will be tour buses and tourists everywhere.

Since you only have a week you might want to add Delphi to your list. It can be combined with Meteora. Same strategy there arrive in the late afternoon visit the museum find a hotel in the village preferably one that looks down the mountainside all the way to the gulf of Corinth. Next morning get to the site at opening. You will have the place virtually to yourselves for an hour and a half before the tour bus crowds arrive. By then you will be high up in the site which will give you another hour and a half of peace.
Delphi and Meteora https://www.flickr.com/photos/stanbr54/albums/72157698930270992

You probably have sufficient time to visit Ancient Nemia and Ancient Corinth plus a stop at the canal on this week.

I think you are seriously shortchanging Athens. To see the central historical area takes a hasty two days and to be done decently three. Drop a couple of days from your mainland plan and add them to Athens.
You probably won't see all this in a week in Athens.
Athens http://www.flickr.com/photos/stanbr54/sets/72157632121475515/

As an alternative, as already suggested, refocus your mainland plan on Nafplio. It is a lovely city with a waterfront location and an old town area. Its possibly the prettiest city in Greece. There are numerous ancient sites nearby so Nafplio makes a good base to explore. Corinth and Nemia are both close as well.
Nafplio and Peloponnese http://www.flickr.com/photos/stanbr54/sets/72157632094108982/

In 2017, we had ten days to spend seeing Greece outside of Athens and the islands. We included Meteora. On the long drive up (from Delphi) we wondered if we'd made a mistake, if the time would have been better spent enjoying one of the other sites we visited or seeing something closer to Athens, but once we got there we're so glad we did. Totally worth it! You don't need to see all six major monasteries - two or three will do -- but there's nothing like them and the scenery. We stayed at the Pyrgos Adrachti hotel in Kastraki. Got a room at the back of the house with stunning views of the pinnacles at a ridiculously inexpensive price. Two years later, we still talk about this being one of the highlights of our trip.

Thank you all very much. We are still waffling about the length of our trip,but this has helped us prioritize.

As “Shoreline” said in post, the drive is totally worth it! When we traveled last September, the highway was largely unoccupied, which made for a stress free drive. We also stayed at Pyrgos Adrachti, and found it to be an amazing bargain! The town of Kastraki is small and charming.

We booked 2 tours with “visitmeteora.travel”: one sunset, and a morning hike the next day. We paid approx $120 total, for two of us. They picked us up at the hotel, provided very in-depth and engaging commentary, access to 4 or 5 monasteries, and views we’ll remember for a lifetime!

We are so happy we chose to rent a car a drive ourselves, as opposed to the rail trip.

I've spent nearly 20 weeks in Greece in the past five years and consider Meteora to be my favorite place to have visited.

Renting a car and driving there is no problem and i think it's more like a four-hour drive. If that seems daunting, give strong consideration to breaking up the drive by including Delphi.

I would spend two nights at Meteora and endeavor to see all of the monasteries (which will require all of one day and a small part of a second). The bus tours and crowds all depart in the afternoon and you'll have the charming village of Kastraki largely to yourself in the evenings.

There are a great many other places you could enjoy whilst connecting Athens to Meteora but Delphi seems to make the most sense. Again, a lot of bus tours zip in and out during the day but the village at night is rather pleasant and the setting is remarkable.