Went to Villamoura early 2000's, my lad was 2 and stayed at a hotel at the beach end of the Marina. Saw another British couple with a kid same age as our lad at the play ground in the hotel, so exchanged pleasantries with them a few times. We went out around the Marina one night, with our lad in the push chair and part way around we saw the other couple in a restaurant, without their kid. They had left him in the hotel room and seemed surprised that we were surprised they'd done that. This restaurant, was a good few hundred metres from the hotel, which in itself was large / multi-story, I have no idea how they thought that was acceptable.