I''ll play the devils'' advocate. This sounds like an easily won civil and/or criminal case.
The skipper must have been somewhat competent as the children were in PFDs.
The design of the boat ABSOLUTELY caused the accident, otherwise we would not be having this discussion!
Most of us can handle just about any simple power boat (MAC 26 included) without any special knowledge. If the owner didn''t brief the skipper about the extreme dangers of improper ballasting, and the boat didn''t have some kind of clear warning at the helm regarding special knowledge to safely operate the vessel, off we go to court!
The boats owner and Macgregor are going to pay through the nose!