Using a pet candy should just consume one without dialog, the user can still choose to spam if they want. Only for eggs it makes sense, because eggs aren't used for anything but consuming candy. So please do not remove the dialog when feeding eggs.
Most people level their pets either slow or through the NPC. Anything else is just too expensive. So please, one candy at a time. Eating too much candy in a short amount of time makes you fat anyways. c: