If you think it plausible that not one, not two but seven individuals, all seemingly loving parents and including a grandma, would all agree to cover for a man who they knew had callously disposed of his own child's body simply to save their own skins, and then not one of them break ranks for 11 years, then that is your prerogative, but I think it is a highly unlikely motivating factor and a highly unlikely scenario, especially when the consequences of being found out in such a plot would be far, far graver than any consequences derived from "guilt by association" in the accidental death of someone else's child (is that an actual prosecutable crime in Portugal?)
There are a few assumptions there.
That 7 people all knew what had happened to Madeleine.
That what they knew was that a man had 'callously disposed of his own child's body '
That the child had died in an accident.
The evidence says that the McCann children didn't sleep through the night. Their parents told us that there was waking and crying on two occasions; Tuesday and Wednesday. According to a neighbour there was prolonged crying on the Tuesday.
If the child checking was less frequent than it should have been, it was in everyone's interest to 'beef it up'.