Strongly disagree. Not sitting a child next to a parent is unconscionable, and forcing parents to pay to ensure that this does not happen is penalising them. Your suggestion is manifestly UNFAIR on parents.
we we could extend the unfair logic to all seat assignments. Using the same basis I could argue that the same applies to teavelling with a child aged over 12 or a very elderly family member who needs reassurance such as my 98 year old nana. I’m lucky I have status but under the current BA seat selection policy some people are being discriminated on the grounds of being childless.