Obviously not during a service(!).
Here's the scene:
Fine medieval church in a small market town. Sign on church door that says "The church is open to all visitors". It's market day so many people popping in and out to see the architexture, buy a card, light a candle..
I go in with my 3yo DS who likes to run to the back the church, stopping to talk shout about things on the way, then run back to the front area (near the door), where the children's door is so that he can look at books, play with Noah's Ark toys there, etc. He tends to shout when he speaks at all, so from a stranger's perspective, you could say he's running and shouting...
As he runs back, a sour faced old bat old lady sitting in the pews, stands up and shrieks speaks sternly "Excuse me, this is not a playground!"
So I apologised and left...DS kept asking why we had to leave and I said it was because the miserable old hag old lady didn't like children.
But I haven't set foot in the church since, don't want to cause offense, can't get over the feeling that churches are really only for the old and solemn and miserable, not for lively young children.
Or was I outrageous to ever take my unruly DS in, especially as we are contented, resolute unbelievers? I just felt the church was part of DS's heritage and even if we are slack secularists humanists, I didn't want churches/religion to seem like a foreign culture to DC (hence why we used to visit the church fairly frequently).