Early stages of planning but want to know how you organized your trip? FYI, not doing a cruise. Would be flying into Athens, spending a bit of time there, and then some of the islands.
Just went there for my honeymoon. It was a short one because of work obligations (I REGRET THIS) - we stayed in Athens except for one day trip to Hydra. It whet my appetite, I'm dying to go back now and spend time at the islands, as well as some of the things we missed from being in Athens such a short time (and one of the days was a national holiday so everything was closed one day.)
We went independently- not as part of a tour group- and stayed in a decent 3-star hotel near Syntagma Square - it was a good area for walking to the various fun districts. Took a half-day tour of the city by bus that included the Acropolis which I'm ultimately glad we did, although the particular tour company wasn't the most organized or well-executed. I wish I'd done a little more research before selecting that tour. (The tour was through Gate One Travel which I think I can mention here because I'm not giving it a positive review AT ALL. Definitely shop around!) There are a million tour options, so just avoid that one and read your reviews before deciding on one if you go that route.
The ferry to Hydra was pretty miserable - very difficult to find where it disembarked, super disorganized, and then once we were seated, it was unairconditioned, you weren't allowed on deck, and windows didn't open, and thus we absolutely sweltered for the whole 2-hour trip. We got luckier on the way back as the a/c worked on that ferry. Hydra itself was charming and we had a lovely walk along the coast.
All in all, a great time - great food wherever we went, absolutely gorgeous weather (first week of May.) Athens was very walkable, and the few times we needed a cab, although Uber works, it just gets you the city's regular yellow taxis, so something to keep in mind.