We had a great time in the Cava D'Oro. Our s/c apartment was basic, and we barely had enough cups, glasses etc. (take your own tin opener) but it was very clean - the sheets were changed several times a week.
There are a couple of things you should know if travelling with small children & babies: (1) the highchairs promised in the Sunset brochure don't exist - we made do with reins & the dining chair, but with glass topped tables it's a bit dangerous; (2) the pool is lovely but the 'shallow' end is 1 metre deep so it isn't suitable for small non-swimmers to play without armbands.
Other than that we loved it. Ignore the warnings about aircraft noise - we never noticed them. The beach is safe and nice, though if you have a car it's well worth the drive to the paradise of Garakas beach.
We ate in many places in Kalamaki, and Zepos was definitely our favourite and we went there several times. We loved the food, location, atmosphere and the service - our (slightly fussy) four year old son was treated like a prince, and loved being called 'sir' by his favourite waiter.
We enjoyed Stanis and Michaelos, although I thought that Michaelos' high reputation makes it too busy to have a nice atmosphere. Try Michaelos when it's quiet, by all means, but don't miss Zepos.
We would definitely recommend Merlis. They're good value for money and convenient (if you are anywhere in the vicinity of the Cava D'oro), and really helpful. Our car was clean as new (though only when we got it!).
We had a slight hitch, as when we came to collect the car they didn't have the baby seat we had booked, but this was sorted as soon as they could, and Julie did offer to give us another car after our rental was finished to make up for the time lost.
We booked over the internet, and the price was exactly as quoted - no added extras for the baby seat, booster seat etc.
We saw a lot of the island, and it was well worth the money.