None for the 2 year old. Perhaps a stern telling off for the 4 year old, but they are both too little to comprehend what they have done.
You left two infants with marker pens. Smart move!!!
My daugheter and her friend did a similar thing whenthey were very little. The adult in charge of them felt very silly, but made a joke of it.
And yes, it could be much worse! An old friend of mine had a nightmare scenario when his boys were little. They were visiting some friends one day. The boys went upstairs to play. After a while the boys came downstairs in a panic. The adults rushed upstairs, by which time the room where the boys had been playing was on fire! They got everyone out and called the fire brigade, but by the time the fire engine arrived, the top half of the house was engulfed in flames! There ended the friendship between my mate and his friend. The guy who’s house it was was a solicitor, but you wouldn’t think a solicitor would be stupid enough to leave matches lying around in a house full of very young children would you?