Exactly. They can visit you. Why couldn't his sister and/or niece have done that and isolated with them for 14 days. Ordered shopping online for them all and helped out with childcare.
At the very worst the sister or niece should have collected the child and taken them to Durham to the second house near the grandparents. Even that is very iffy in case the kid is just not showing symptoms, but it's vastly better than two already ill people spreading around
With the wealth they have it's not beyond them to do that, even if they suddenly come out with "none of them have a car"
And with the contacts Cummings has there's not a chance he'd be struggling to get a supermarket delivery slot for shopping for him and his wife.