@ShouldntHaveBeenSoHasty
You're not being unreasonable. My DCs school used to do this... When they were at senior school, there were 900 children in the school, and you could literally count on the fingers of two hands the amount of non white children. Four mixed race children, a couple of black children and three Asian children - out of 900.
There was a big billboard, maybe 10 foot high and 20 foot wide by the front gates at school, with seven children on it, jumping up and looking happy and having fun and smiling, with 'COME JOIN OUR WONDERFUL SCHOOL' emblazoned above them ! SIX out of the seven children were mixed race, Asian or black. Literally six out of the seven children. ONE white child. Even though only 1% of the children in the school were non-white.
It genuinely smacks of trying to desperately be politically correct and it's pathetic. It's also giving a wrong impression of the school and suggesting there's a massive complement of non white children there, when there's literally less than 10 out of 900.
If they want to be more inclusive then try to encourage many more black and Asian children there. Don't do fuck-all to encourage them to join your school, have 99% white children, and then pretend you're all inclusive and politically correct, by having just ONE WHITE child out of seven children on your colossal billboard.
It's like these big companies - like the BBC. They promote how 'woke' and politically correct they are, (along with the producers of most adverts,) because there are so many non white faces on the TV. Yet you rarely ever see any at the top of the company, and running the place, and very VERY few of the big executives will be black, mixed race, or Asian. It'll be run by overprivileged white men. Want to be more fucking inclusive? Stop letting the vast majority of your high, privileged, and super well-paid positions be taken by white males.
Going back to your dilemma OP. I would absolutely take away the consent as well, seen as they're letting businesses use your childrens images to put on their Facebook pages!!! What the actual fuck have I just read? Definitely withdraw consent.