All-you-care-to-eat includes not eating…If you’re eating at a restaurant that is a buffet or the food is served family style, there’s no “just sitting and not eating anything”. You’ll pay for everyone three and older, even if someone does not want to eat. It’s not up to the server to keep track of who is eating and who isn’t. If there is a reason why one person can’t eat, ask to speak to the manager. Exceptions are sometimes made. If the reason why someone doesn’t want to eat is that they don’t like any of the options, talk to your server. There could be some off-menu choices.