There should definitely be some sort of action against them, but I'm not sure that a corporate manslaughter charge is the way to go.
From what I have read, I'm very unclear as to what this "housing society" actually is. It seems to run like a co-operative, and I have no idea if it's ultimately answerable to the Housing Corporation, the Dept for Housing and Communities (or whatever it's called this week), or any other body.
What it needs is to be put into some sort of special measures and be forced to sort out the way it deals with repairs/maintenance generally and mould issues in particular.
But tbh, I'm surprised that something like this has never happened before. I've worked as the clerk to housing & housing management committees in 2 different councils, and the issue of mould in properties was always coming up. I've also been involved on the other side, in housing advice agencies, working on disrepair cases against councils/HAs. For every expert that reported that mould issues were due to inadequate maintenance, insulation, whatever, there would be another that blamed it on tenants not opening windows, drying washing indoors or not cleaning adequately.
I really hope this is a wake-up call for all landlords, social and private, that they need to take this problem seriously and get it sorted.
And my heart absolutely goes out to this family and their beautiful boy.