Why are you conflating issues?
If patients are waiting for medication or to go to the toilet then they ward is short staffed (which would be made worse if the parents weren't there to supplement the nursing care by taking child (patient) to the toilet, washing them, feeding them, entertaining them.
They aren't breaking the 2 visitor rule or staying past visiting time - a parent is encouraged to stay on the paeds ward. That is the norm. And meals are usually served by domestic staff, with nurses helping so giving the parent a meal at the same time as the patient isn't adding to the work load.
Getting me, as a patient, to sit with my sister when she was on the ante natal ward in labour, was solely done to lessen the work load on the midwives. Getting me to get my dad on and off of a bed pan and commode when he was in hospital was done to lessen the work load on the nurses ("Oh his nurse is on his break. Can he wait until she comes back? If not the sluice is over there if you want to get him a bed pan"!!!!)
So, given that visitors are very much relied upon in some areas I do think that the NHS should consider providing food when the relative stays in with the patient.