This summer we stayed in July/Aug school hols, the only time we saw a child was late afternoon twice, when a couple came with their small child (think they were Polish) they had a quick swim and left after 10mins both times.
The Mathraki is very quiet during the day just a few couples around the pool, Bill is not very keen on the beach, although we do go often, he just prefers the peace and quiet of the pool and reading is my hobby so we seem to spend more time there.
We have breakfast about 10.30 which is the best we have had anywhere, and then a snack late afternoon. All very good value and delicious, Nic and family provide an extensive menu and a good bar.
Rooms are typically Greek, very clean with a kitchen equipped to cook full meals if you want to (not me) ha ha.
The rooms all have a sea view, with sunsets to die for, the upper floor are the best view. There are only 16 rooms so it is not overcrowded.
The Mathraki has lots of repeat visitors which tells you a lot.
Hope this has been helpful, just ask and lots of people can give you info about Kaloudis, we only visit there for a drink but it is nice and very good for couples and families.
Val x