We stayed at the Delfinia in the hotel (they also have bungalows) for a week with 3 small/medium children and my fairly active in-laws. The hotel proper was very pleasant; the rooms were not that large but very well-maintained and clean, the lobby, bar, and breakfast areas were extremely pleasant and airy, with lovely views. The bathrooms were a pretty good size, and had hand-held showers in bathtubs with sliding doors. The air conditioning didn't work very well in one wing, but the hotel moved us to a different room without difficulty. Breakfast was very ample and fresh, and the staff were pleasant and helpful. The grounds were, as advertised, lovely, with all sorts of flowers, fruit trees, vegetable gardens, etc. I would say the price was perfectly in keeping with what we received.
The high point, for us, was the pool area, which has a nice salt-water pool (just the right depth for our children), a ping-pong table, and a taverna with some of the best food on the island (not to mention the ice-cream). The pool and taverna had a magnificent view of the town of Molyvos, and were immediately adjacent to the beach. The water was crystal clear but cold (and thus the kids preferred the pool), and beach was mostly pebbly, although there were patches of sand.
The downsides were minor, specific to one's physical condition. The walk down to the pool/beach area was quite steep, involving pebbled walkways and stairs. My in-laws could just manage it, but some might find it a bit far. Between the hotel and the pool area was a soccer field that was in use by what looked like local kids most nights - there was a bit of noise associated with this, we found it pleasant but some might not (but the rooms were very well soundproofed, and with the door closed it was not noticeable). Finally, the Delfinia is located a couple of km outside of the town of Molyvos. One evening we tried to walk there for dinner, but the sidewalk gave out at a bridge with a blind curve, and with children and the elderly we decided not to risk it. I would say the walk would have taken us half an hour or more had we continued. We had a rental car, so for the most part this wasn't a problem for us.
The hotel had a range of clientele, several other families with children, but also both older and younger adults. All in all it was a very pleasant and relaxing place to stay.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC