But 50 yards away on the other side of the swimming pool, the group's children were sleeping alone. In the bedroom of one ground floor apartment was Madeleine, the McCanns' three-year-old daughter. Her twin brother and sister, Sean and Amelie, two, lay in cots either side of her. They had been tucked up at 7pm. Half an hour later the McCanns had joined their friends for dinner at the tapas bar.
What happened next has mystified the world.
At 10pm Kate McCann got up from the table to check on her children. She slipped in through the patio windows to find the twins safely asleep - and her daughter's bed empty. In tears and calling out Madeleine's name, she ran back to her friends to tell them: "They've taken her, they've taken her."
Madeleine has not been seen in the 100 days since May 3. Last night Portuguese police said they were concentrating on what they call the "missing hour" before Mrs McCann found her daughter gone. They say it is possible that she was kidnapped after her father last checked her at 9.05pm and her mother's terrible discovery.
This week the donations from the public to a Madeleine fund, financing the PR campaign and global search for the little girl from Rothley in Leicestershire, was nudging £1 million.
More than 50 million people visited the Find Madeleine website in the 48 hours after its launch.
Nothing like this has ever been seen before, and probably never will again.
The campaign has been organised by the McCanns, both 38. Today they believe their daughter is still alive and was abducted by a stranger. Whether the motive was paedophilia, the sale of Madeleine for adoption or even the trade of her organs, they have no idea. Nor do they speculate. As Mr McCann wrote on his website the other day: "The Portuguese police have assured us on numerous occasions that they are looking for Madeleine and not a corpse."
The reluctance of Gerry and Kate McCann or their friends to speak publicly, or in any detail, about the minutiae of the evening has fuelled the controversy, although they insist it is illegal in Portugal to comment on any police investigation.
In another uncomfortable development the Portuguese press, including the respected newspaper Dairio de Noticias, has claimed that interviews given by the McCann group to police contain discrepancies. Their stories and the timings of their movements on the night do not tally. Furthermore, emails and phone messages sent between the group - and intercepted by the PolĂcia Judiciaria and British detectives helping the inquiry - are reported to contain conversations that contradict earlier statements.
One question being asked is why didn't the parents put their children in the evening creche which is open until 11.30pm? Why didn't they hire a babysitter, bookable at the Mark Warner reception desk?
In a further twist, locals now claim that Madeleine did not always settle well. One evening they allege she ran away into the paths between the apartments, hiding for half an hour when it was time for bed. Whatever the truth, to begin to unravel the mystery one has to go back to the seemingly carefree days at the start of the holiday.
Gerry and Kate McCann and their friends are like-minded people, with children of similar ages. And they knew each other in the Midlands. Mr McCann is a consultant cardiologist at a Leicester's Glenfield Hospital and his wife is a GP.
Until recently Dr Oldfield worked at Leicester general hospital. David Payne is a senior research fellow in cardiovascular sciences at Leicester University and his wife, Fiona, is a doctor. Another of the holidaymakers, Dr Russell O'Brien, also worked at Leicester University before moving this summer.
Recently they all went to Mark Warner's in Greece where they had devised a plan of leaving their children to sleep while they had dinner nearby.
As Mr McCann explained: "The distance is so small, it was so close it was almost like having dinner in your garden. What we were doing was rigorous with multiple people checking at regular intervals."
There is another conundrum too. It concerns the sighting by Jane Tanner of the man carrying a child. He was wearing beige trousers and smart black shoes. Her report is taken seriously by police.
Yet a British holidaymaker, Jeremy Wilkins, has given a deposition that does not support her evidence. He knew Mr McCann because he played tennis with him, and was walking his eight-month-old son in the night air when the drama unfolded.
He says that he met Mr McCann, who had come out of his apartment at 9.05pm, and had a word with him. Soon after that Jane Tanner would have crossed paths with Mr Wilkins and his baby.
Mr Wilkins says he saw no man carrying a child or Jane Tanner herself. "It was a very narrow path and I think it would have been almost impossible for anyone to walk by without me noticing," he said.
So today the questions remain. Was Madeleine kidnapped or killed? Or unwatched, did she simply walk out and get lost? How could there be a break in with a jemmy through metal shutters without waking the twins or alerting a passerby?
Someone, somewhere must know the answers.