Cate, Hate to say this but you are not quite correct.
The law states that under 3's must always be in a child seat unless they are in a Taxi or Private Hire vehicle.
So I am not able to drive the family, but if they can afford it, an immigrant more used to driving on the other side of the road, moonlighting as a minicab driver, is fine, otherwise they have to walk.
The response from the government representative was:-
I take the point that you make but there's not much I can say. We do understand that lifts cannot be offered in the same way as they were previously. And we are always aware that not everyone has access to local transport or their own car.
But as the use of child seat/booster is mandatory, then it is logical that we cannot leave things so loose that we open up cracks that some will seek to exploit.
As you say, where children are under 3 years, they cannot travel without baby/child seats. For those 3 years and over, if there is no child seat/booster, then where there is "unexpected necessity over a short distance" an adult belt will be the alternative in a rear seat. But 'unexpected' and 'necessity' mean just that and a court may not always agree what qualifies.
Makes me wonder how I managed to grow up and later how my 5 kids survived as we had a microbus with no seatbelts and never a problem.