My font of choice for picture books is...

When I was in first grade, in order to go out for recess, I had to read the letters printed on footprints that led the way out the door. The first letter I learned with a circle and a stick was a "b" so I, as an undiagnosed dyslexic, saw all letters with circles and sticks as "b." Needless to say, I didn't make it out to recess often. I felt really really really dumb. 

When I started writing books, I wanted to find a font that was easy to read. To me, the most important thing about the font is that it's easy to read. One that had circles and sticks, just like the ones I struggled with, that kids learn when they first learn to read. That's why I use Quicksand. 

For those onomatopoeia words, I do use other fonts, but tend to use sans serif typefaces that use circles and sticks.