Hi there,
So as @liaifat85 points out the step down is the way to go here, Also just to add IF your pulling High current for short period with S3 you need that BIG capacitor next to the 5V in.
for some reason I find it’s easily browned out and resets under those conditions. just FYI
the Converter may also provide some with the 470uF part.
HTH
GL 
PJ 