Child's note is a paper note in Fallout 76.
Location
The note can be found in Palace of the Winding Path, inside the highest gazebo on the pond.
Transcript
mommy said I cant play at the tempal if theres smok
she said not to play with the scary peeple becuz they ar here to keep us safe from more scary peeple
so i took my baer frends and we ar playing with toys here