Gosh that is rather like my kids. All three of them getting into mischief and not noticed for a while. I wonder if they opened the door themselves too.
What day was it I wonder? Between Monday and Wednesday, Gerry says. Monday 30th nothing is reported, but the children returned to their clubs later than was usual; Madeleine at 15:15 and the twins ten minutes later.
Tuesday 1st is when Kate said they went to the beach for ice cream and came back later than normal, but they were signed into their clubs at 14:30.
http://www.mccannpjfiles.co.uk/CRECHE/Processo-pdf01pages108-118%20[112-120]/processopdf01page118-CrecheRecordsJ.jpg
If Kate got the day wrong they may have been at the beach on Monday, not Tuesday. This fits with Steve C's statement too, he said he saw them there on Sunday or Monday;
that you saw them both playing sport and they passed by you at the bar on the beach and this was Sunday or Monday at about mid day.
SC: Mmm, mmm.
http://www.mccannpjfiles.co.uk/PJ/STEPHEN-CARPENTER.htm