If eating out with a 3 year old is challenging, you're doing something wrong. Lately when we go out to eat, if we hear screaming kids we ask to be seated as far away from them as we can get. Eating out is a treat and should be enjoyed without disruptive behavior from anyone (once we had to ask a middle aged man to please lower his voice & the management both apologized and thanked us for addressing him). Yes, a little baby is going to cry and that's understandable, but if it's continuous and loud, the parent should respect others dining and step outside/away until the infant calms down. A toddler should be taught and disciplined to behave appropriately in a restaurant or any public place. You can't even grocery shop anymore without children running and screaming through the aisles or having a fit if they don't get what they want, while the parent seems oblivious. On the other hand, thank you for asking about playgrounds in restaurants. Letting them play is much better than ruining other customers' outing.
@ChloeW : Do you have children?