Hi Cheryl!
Finding the best answer involves Trade-offs -- ideally there would be an isle(1) 1 hour by ferry (2) gorgeous Beach (3) lodgings right on the sand (4) enough facilities open in, but no crowds. My thoughts:
• CLOSE but no CIGAR -- AEGINA = 1 hour ferry but its main beach, Ag Marina, is mediocre. ANGISTRI is 1 hr, but may be really shut down midweek in OCt, HYDRA, as they say, no beaches.
• GOOD BEACHES but NOT Near, no beachside lodging (or mostly closed) -- ANTIPAROS, FOLEGANDROS, MILOS, SIFNOS, etc etc
My suggestions:
(1) SERIFOS -- and specifically on Livadaki Beach, right over the hill from the port, only TWO places on entire beach! here's amateur snapshot of the beach -- a few more fixed umbrellas now, but otherwise unchanged. 30 feet from your patio, to sand! http://static.panoramio.com/photos/original/14370946.jpg
CORALLI BUNGALOWS (love it) - http://www.thesaurus.gr/hotels/serifos/coralli_bungalows/coralli_bungalows.php (advise booking thru this agency; fastest response) ALEXANDROS-VASSILLI (family-run rooms & wonderful taverna) http://www.vacation-greece.com/hotels/cyclades/serifos/alexandros-vassiliki/
TRANSPORT -- 5 hours Alas. 1 X Day: MON OCt 12, a "Regular" ferry 14:55 (2:55pm) arrives 19:35 (7:35). Return FRI 6:45pm or SAT 3:30.
(2)** NAXOS** -- Stay at Ag. Giorgios (St. George) BEACH, directly Adjacent to PORT TOWN. Lots of Sightseeing but u dont need to do ANY; just sunbathe, walk beach, walk 10 mins into port town's seaside tavernas by night. HOTELS Directly ON SAND - Asteria, Studios Kalergis,
FERRIES -- Daily: 3+ hrs or 5. OUTBOUND - Catamaran 7 AM10:20, Ferry,7:25 AM- 12:40 or 5:30pm- 10:45pm Return: 9:30-3 and 6PM-11:30 (ferry) or 2:25-5:30PM (cat). Trade-offs: Cat is faster, but $$ and Erpy in rough seas;
Reg. Ferry slower, but has outside deck & you can snooze indoors in comfy seats.
FLIGHTS: ATH - NAX Mon OCt 12: 8:50AM (45 mins), €109. RETURN - FRI 10/16 9:45 AM or 2:05PM, €88.