You use the phrase, 'as far as I know' which means that you simply cannot eliminate the child's possible particular needs.
I said that as I cannot know for sure that he is vulnerable as defined by the government guidelines. Do you have any information to the contrary, for example that Cummings' son is defined as vulnerable which means his is:
aged 70 or older (regardless of medical conditions)
under 70 with an underlying health condition listed below (ie anyone instructed to get a flu jab as an adult each year on medical grounds):
chronic (long-term) mild to moderate respiratory diseases, such as asthma, chronic obstructive pulmonary disease (COPD), emphysema or bronchitis
chronic heart disease, such as heart failure
chronic kidney disease
chronic liver disease, such as hepatitis
chronic neurological conditions, such as Parkinson’s disease, motor neurone disease, multiple sclerosis (MS), a learning disability or cerebral palsy
diabetes
a weakened immune system as the result of conditions such as HIV and AIDS, or medicines such as steroid tablets
being seriously overweight (a body mass index (BMI) of 40 or above)
those who are pregnant
people who have received an organ transplant and remain on ongoing immunosuppression medication
people with cancer who are undergoing active chemotherapy or radiotherapy
people with cancers of the blood or bone marrow such as leukaemia who are at any stage of treatment
people with severe chest conditions such as cystic fibrosis or severe asthma (requiring hospital admissions or courses of steroid tablets)
people with severe diseases of body systems, such as severe kidney disease (dialysis)
And if he was, then the most dangerous place to be would be in a car for 6 hours with a person with symptoms. Were he actually vulnerable (as defined by his own guidance) the child should have been removed from a household containing self isolating people to a safe place (again according the Cummings own guidance) - but he wasn't - he remained with symptomatic people for 14 days including a 260 mile car journey in a small confined space.