Ok, to spell it out, the message created a vision of a crowded platform, full of fit individuals travelling alone and with just one family group, with a child in a push chair. Taken literally, the message might suggest that everybody should rush over and, for their own safety (not that of the child), gather around the push chair and hold on tight.
In my mind it’s comparable to the notices on London Underground by the escalators, stating that ‘dogs must be carried’, which I know many people find amusing. What if you haven’t brought a dog, do you have to use the stairs?
Apologies however if, in this case, not everybody shares the amusement.
PS: an afterthought, the above joke aside, is it maybe insensitive of the railway company to assign equivalence between pushchairs and wheelchairs? I’d think twice, as a bystander, before grabbing hold of somebody’s wheelchair if the user seemed competent and clearly did not need or want me to do so? It might even backfire badly if, by interfering, I caused the wheelchair to deviate from the user’s intended path and into some other danger.
Edit: added ps.