30th Wedding Anniversary Trip

Step one, determine how much time you wish to spend in Athens. Step two, determine if you want an island or a mainland destination (latter requires a car). Then, you’ll know what you have time for and advisors will know how you wish to get there.
There are a lot of islands, no way around that, but I think it takes a lot of the fun out of it to not select the one that calls to you. Do neither of you have any inking?

Thanks for the reply. We were thinking about a couple days in Athens when we arrive and then 2 islands for 3 days-ish each, then back to Athens, then home. Looking for islands with history, good food, beaches, and minimal crowds.

Since you are travelling in high season minimizing crowds is going to be pretty much not possible.
I know its a long haul across the Atlantic ( we actually make this trip form the west coast) so we always make a connecting flight within 3 hours of arrival in Athens. Its a crazy long day but after 17 trips to Greece we always want to get to our first island ASAP in order to get over jet lag in a more laid back atmosphere compared to doing it in Athens.

Get out to your chosen island on day of arrival and leave Athens to the end of your vacation. Two reasons, you will have some experience on things work in Greece and you will be in Athens a couple of days before your return flight .

My plan gives you one extra day on your chosen island.

If this were us we would choose the island of Naxos. It has an airport so you do not have to spend hours on a ferry. It has a lovely old town with waterfront promenade and a Venetian era Kastro. It has great beaches and mountain villages to explore. It needs at least a week to fully appreciate.

Since you are in high season I suggest you look for a hotel on the west coast,

There are lots of good hotels and several good beaches in this area. It will be busy but not as busy as Naxos town.

Here are some images of Naxos. All are in shoulder seasons.
Naxos 2025 https://www.flickr.com/photos/stanbr54/albums/72177720329571437/
Plaka beach west coast https://www.flickr.com/photos/stanbr54/albums/72177720299954668/

For once i"m not going to echo Stanbr -- we usually compete on who loves Naxos the most... but I have a different idea this time, With only 10 days, be transit-efficient, no backtracking. Since u must be in Athens anyway the night before departure, do ALL Athens time Last, And in High Season, a crowd-avoidance plan is -- choose islands without airports. Try 2 beauties, SERIFOS & SIFNOS. #1 is small cutie, stay on lovely beach near port, few sight-seeing "musts".. great place to just relax. #2, only 30 minutes away, has Stunning beauty, hillside villages, sandy beaches, amazing walks - AND not yet spoiled by exploitation to serve super-rich. Go before it Changes!!!

DAY #1 -- JFK Delta nonstop arr ATH 10:30 am) Take 50 minute taxi/car service ride to PIREAUS (seaport). High-speed ferry (large, vehicle-carrying) de[ 3 pm for SERIFOS, arri 5:40 pm. Check ahead for nice cafes near ferry ramp, for relaxed lunch.

SERIFOS -- Fab beach, Livadakia, just over a hill from Port -https://1001beach.com/en/europe/greece/serifos/livadakia -- in July it can be crowdy but if you can book one of only 2 places directly on beach, you'll have your own space: (1) https://www.corallibungalows.gr/ or(2) family-run guest house http://www.vacation-greece.com/hotels/cyclades/serifos/alexandros-vassiliki/ To dine, walk down beach, over hill, and presto! port beach, with waterfront tavernas where chairs sink in the sand. Rest, recover for 2 days .. maybe take bus up to stunning top of isle "chora" & walk back down. Next day sail to SIFNOS (30 mins)

SIFNOS - a less-discovered Gem of Cyclades!! This fine site tells ALL -- click every link! http://sifnos.e-sifnos.com/index.htm -- Stunning villages, with white-cube house strung across hillsides like pearl necklaces. This map has details-- https://www.insifnos.gr/images/sifnos_map_bg.jpg The MOSt enjoyable isle for walks, in lovely flagstone walkways.
Notable for gourmet cookery, pottery crafts (100 years ago it was Greece's pottery center, now revived).

BEACHES -- 4 main beaches -- at Port of Kamares, then Platy GIalos, Vathy, and Faros, plus swims off rocks below snowy Medieval town of Chora. Many people prefer staying at beach places, If I were to stay at a beach, here's my favorite place in Platy Gialos -- Giannakis Studios -- https://www.giannakas-studios.com/en/location.html -- but probably too late to get rooms there. -- best hotel-location option is Platy Gialos Hotel, right on sand, kingsize beds, beach views. There are many Fans of KAMARES for both swims & stays. Port has best sunsets, but its main road circling bay TOO busy, beach too near pier, and town feels closed-in (wedged between 2 hills). I stay in hills, bus down for sunsets & dinners.

HILLSIDE CHOICES -- Divine valley & sea views, good bus network or car for beach days. Charming nightlife in Appollonia clubs & cafes, music along lanes I stay in one of 3 linked "necklace" towns -- Appollonia, Artemonas. Ano Petali -- hop a bus to Platy Gialos or Vathy. An Appollonia upscale hotel is Petali Village (pool, spa, staff) .. (its right across lane from my budget gem, Nikoleta's Rooms, vine-covered patio... no hotel services). In linked town of Artemonas, Hotel Artemon, on square, is longest-established Sifnos hotel (1968), so furnishings are traditional, rooms are spacious, walls are thick, and service is caring. Artemonas square has several notable tavernas (restaurants) just steps away... and these 2 towns are center for both busses & hiking paths... latter are paved & signposted!

SIFNOS is packed with history, churches, arts, traditions -- explore website to discover treasures, days will Fly By.
ATHENS -- Many will have suggestions here; my only major tip is: look for hotel SOUTH of Acropolis... away from noisy busy 6-lane avenues, instead has lovely pedestrian promenade, low-rise buildings, greenery and quiet cafes.