Yes, kids cost the same as an adult, they still use beds, make mess and eat food.
The only way it is slightly cheaper is when they are the 3rd or 4th person in the room or they have a special like kids sail free.
We had our 11 month grandchild cost the same as her parents in a room. No ship food or kids club but she did still make mess and need a crib.
We have been lucky and have never missed them, however it does seem to happen often. Big seas or winds may delay arrival or restrict access or cause an earlier departure. Then there is always the possibility of the hull requiring cleaning or a medical emergency.
If the sounds are a must see or must do, visit on a land holiday separately or pre or post cruise.
There were a few events.
1 We had to switch gates and planes just as boarding commenced. So slightly delayed as bags had to be transferred.
2 Our shuttle was pushed back 3 hours due to the shop coming in late and we had a bus full of Buddy cruisers, it was fun though.