Actually (don't get me started) parents these days seem to prioritise their obnoxious little darlings' interruptions: "Yes of course sweetheart [how hugely clever of you to even be able to speak. I'm so so proud and I'm sure the adult I'm talking to will understand my child always comes first]. Sorry, I'll continue with our conversation after I've given Prunella another doughnut"... or maybe they've trained Prunella to always interrupt conversations with me. Hmm.
But back to the waiter, the answer is always "Yes it's fine [now please go away]". We're not going to tell you it tastes like shit in case you tell the kitchen and they piss in our dessert. We'll post what it was like in TripAdviser later.... So sod off and don't interrupt us unless you're taking our order or bringing us food, drink or the bill.