July trip help to narrow itinerary (begins in Sicily so posted a question there also).

Crete is a country all its own (170+ miles long!!), I know some people who spend a month there and never see it all. I have been there 5 times, for at least 5-6 days per time, and still have seen less than half of it.

I think you need that time on Naxos since you are doing so much travel before Greece, and then a ton of driving in the Peloponnese. It will be your best beach experience .... and a chance for Teens to be on their own ... the rest of the time they're locked into The Family Plan... and often the Family Car as well. In Naxos they can wander safely, it's a famiiy-oriented island with excellent bus service to/from port town every 30 minutes. Just give one of them one of your phones and mandate a periodic check-in. Then you and husband can have a bit of grown-up time as well. In fact, I'm willing to bet that, after this trip is over, you'll look back on Naxos as your quintessential island experience.

NAXOS ACCCOMS: Don't fall for a VRBO or AirBnb just because of price or fancy trimmings ... it's all about location. You need to be VERY near the beach, or your kids will harangue you constantly to drive them places. In July, a good choice may be Ag. Prokopios because it's an excellent LARGE beach w. plenty of sunbeds, cafes etc. A place I recommend there is http://lianahotel.com -- because it's one of the few that is just a few feet from the sands (other places require walking down a busy road for hundreds of yards.) It also has units with several bedrooms, plus a pool.

SANTORINI ACCOMS -- this place is going to be JAMMMED in July and hot hot hot ... So cooling off in the water is a MUST. And the East-coast beaches will be like grills ... made of black grit, too hot to walk on barefoot .. If you stay on the West (Caldera View) side, hotels with pools can be horrifically expensive, with a few exceptions. Again, location is key with teens in mind, try to stay where they can WALK to places, instead of nagging for a ride. Comparisons: OIA this famous "calendar shot" village is super-packed with tour groups from 10 am - 4pm and then again from 6 -9 pm, so unless you are in a superluxe accommodation, the lanes won't be pleasant to stroll, they'll be Times Square at Rush Hour. FIRA, the main town, also gets this invasion of up to 9,000+ cruise crowds from Monday- Thursday. Thus as a avoidance strategy I would suggest checking out Firostephani, above the north edge of Fira Town. It's the "goldilocks" spot... NOT in the mob scene, no tour groups ever, but also not far out and inconvenient -- AND many hotels with Caldera views. See this map http://mapsof.net/santorini/thira-island-santorini-map From Firostephani, you can walk along the rimpath 15 minutes to Fira Town attractions, and for Oia, there's a handy bus stop on the road inland from the rim hotels -- no need for car rental. Check pool hotels and if they're too pricey, I know a darling budget hotel that's only about 30 yards from the rimside path, and has use of another hotel's pool another few yards away.

ACCOMMODATIONS in GENERAL -- PLEASE PLEASE do not delay looking for lodging, because the kind you want fill up months in advance, in fact some may be full already (and BTW, almost all Greek hotels/pensions allow cancellation no penalty if your cancelation is 2-3 weeks in advance, so booking is Risk-free -- if you can't make up mind, book 2, then decide). Also, once you get a reservation, if you need to "tweak it" one day earlier, or later, hoteliers usually will try to accommodate. Another thing; you can research online via a booking agency, to determine date availability and room rates -- but if you THEN contact the hotel's OWN website directly to make a booking, they'll be happier to help, because they save the % charged by the online agency.

I agree with Janet ... slow down a bit, and spend your Greek island time on Santorini and Naxos.

Ideally, if you can get a flight from Sicily to Santorini, spend your 2-3 nights there first. Then ferry to Naxos and have 5-6 days to relax. Plenty to keep the kids busy while the adults recharge and get ready to hit the road again on the mainland.

From Naxos, you could ferry or fly back to Athens. The planes that fly in/out of Naxos are small and seats are limited, so if you want to fly back to Athens from there, book soon.

Many thanks for these replies and for those sent to my personal in-box.
We have switched our time around to depart Sicily and head straight for Santorini, and then on to Naxos.