The problem is many parents believe having a child is a permit to drive like a twat. Hence the correlation between shit driving and “child on board” stickers which usually lead me to expect the car is driven by someone behaving like a spoiled entitled brat.
How about referring to the relevant law?
https://www.legislation.gov.uk/uksi/1986/1078/regulation/105/made
In the case of children exiting cars, permit clearly puts the responsibility on the driver to make sure they do it safely.