I think the recommended tip per person is added to your Sail & Sign account. We prepaid ours, so we didn't have to worry. We tipped room service 3 dollars every morning. We tipped the room stewardess an extra $100.00.....she was great!
On the last night we received an envelope for the maitre de, but we didn't use it. We never saw him. We didn't tip our waiters any extra because honestly the service was average. Many times they forgot about us completely. Extra appetizers we requested never appeared.
We didn't have any children in Camp Carnival, but we have tipped them when our children were younger.
With that said, the tips were delivered to the staff by Carnival from our account. We only tipped room service and the room stewardess in cash at the end of our stay.
Others probably do more, but we didn't.
I'm sure someone else will post other suggestions for you.