Yes. Potential criminal liability should be assessed by the CPS given the truly shocking content of their statements to the enquiry.
Those statements reveal they knew AR was stockpiling an arsenal of murderous weapons & actually saw those weapons; that they knew he was deep in psychosis, highly aggressive, violent, uncontrollable, & filled with hate towards members of the public; & that they knew that shortly before the Southport attacks he had attempted to take a taxi to attack his former school. And yet they concealed all this because they believed revealing it would mean he was taken away.
His mother made a ‘zip it’ sign to prevent relevant information being given to a social worker.
They saw AR leave the house on the day of the attack, knowing he was a risk & might have a weapon, knowing that in the previous two years he’d only left the house on one occasion, that being to try to launch an attack on his school (that’s why as soon as soon as his father heard of the Southport attack he knew it was his son) & yet did not bother to follow him to see him get in a taxi round the corner.
Their statements are horrifying.
These were not parents trying desperately to get help for their son. They were - by the father’s own account - parents concealing the risk their son posed to society. Maybe the criminal law does not permit accountability for this (I have no idea whether any of the inchoate offences would cover it) but it should.