Aeromax Astronaut Boots, Size Large, White, with NASA patches

What size should i choose 4 my 2 year old son ?

According to the information listed, "Small" fits age 3-4, while "Medium" fits ages 9-11? What did I miss?? Is there a size "Smadium" somewhere?

how tall is the shaft. My daughters astronaut costume is short on her so I was hoping to use the boots to cover the lower part of her legs.

My 9 year old wears a size 2. Getting alot of mixed reviews, am I going by age or size? Was interested in the white boots.