Are you choosing July in order to have your trip include the Exact Anniversary date?? Or is it because of job restrictions? If it is the former -- I would urge you to adjust the dates earlier. July is the HOttest Month, it's High Season, and the large crowds could diminish your experience. You'd do much better if you could at least do the last 2 weeks of June -- and from Mid-May to Mid-June would be even better.
Your list does sound like a sample lifted from an online travel (Blog??) source -- probably commercial. Since you have tons of time I urge you to check some reputable travel guidebooks (usually R Steves is good but he doesn't "do" islands -- probably because his in-person tours are mainland). Go to library & take out BACK Editions of Rough Guide, LONely PLanet, Fodors, Eyewitness Greece etc. (The most recent editions are packed with color photos and hotel/restaurant reviews, and very short on destination background & ambience). The older editions are also more candid about drawbacks as well as highlights. You're going to spend $$$ on this trip, so it's worth doing homework not depending on online plugs or Eye Candy.
ITINERARY thoughts (1) 16 days is better - u can do this by flying out on a Thurs afternoon, Returning on the 3rd Sunday. NOTE: in planning you can only count Arrival day as half-day, IF you arrive before noon, and not count DEP day at all. (2) Do Athens LAST -- it's most transit & time-efficient, and also, you get over jet-lag in a slower-paced place, a lovely isle, AND island-time makes you savvy about Greek history & Greek ways, so that in Athens you navigate better, and appreciate its treasures more. (3) you need to be very strategic to be transport-efficient... in order to spend Least time getttng to/from places and Most time onsite, enjoying. So look at MAP, and use Ferry websites like Openseas (current skeds for this summer will show usual links). Plan a route that gets u to isle #1 on arrival day, and final island has flight or 2-hr ferry back to Athens/Pireaus.
ISLE OPINIONS (just personal, but based on 13 Greece visits) SANTORINI - Massively impacted by megacruiser crowd Plus plane-ferry tour groups; fewest ships on weekends, so best bet to come in Th or Fri, leave by Monday; it's mainly about The Famous Caldera View, so can be appreciated in 48-72 hrs; MILOS - once less-visited now "discovered"; lots of beaches but bad local transit, requires car rental; not big on Quaint Villages PAROS & NAXOS - Choose one, stay longer -- Naxos larger, more dramatic scenery & hillside villages. as an Alternative to Milos consider SIFNOS... glorious beaches, hillside towns, walking trailing, boating, history - and because no airport, fewer big ferries not yet invade by mass tourism.
POSSIBLE SEQUENCE? ARR BEfore NOON on a FRIDAY - Get 2pm Flight to SANTORINI - Stay F-Sa-Su Monday Ferry to NAXOS; stay NAXOS M- Fr ; on Sat ferry to SIFNOS for Sat - Wed Aft. ferry ATHENS Wnight - Th - F- Sat. Sunday: homebound flight - Do NOT sked before 10 am or u will have to get up TOOO early to get in line at airport.
