I couldn't and certainly don't with the grand children, even more so than my son.
But, when you look at the risks of all the children between the group, only M and one of JT's children slept in a bed. So potentially the environment wouldn't have posed an hazard to the younger children in cots.
That leaves the two children in beds. JT in her Roggie interview made it clear that she deadlocked the door so her daughter couldn't get out.
So, let's go full circle about your friends. Do they do it with children who are independent enough to go to the toilet, be alarmed if they wonder around the apartment & find themselves alone? And lastly, in a ground floor, public accessible area, leave the door unlocked.
I will be very interested in the trial of Bridger over the disappearance of April Jones, and his rather strange plea of 'probably killing her' ... or something along those lines. Here's a man, friend of the family - talking in riddles and will not confirm where she is. Why?! Surely he is trapped. So you would think, but that's the problem of human behaviour. Expect the unexpected. Then there's the case of Tia Sharp, wrapped in black-poly bags & put in the loft.
Always the case goes full circle. An opportunist abductor, no transport, why take the biggest !