Hi all I've been away for a while but now I'm back!

so after trying on my son's wardrobe I have come to the conclusion that he needs a completly new wardrobe. He will be three in August. We live in Alabama so its warm most of the time for our events but I want to be prepared for cool weather too. So here's what I'm thinking.
Cotton or linen drawers with button on underbody.
Short or maybe long pants in cotton twill probably...maybe wool
Cotton 3/4 sleeve tunic with a white shirt to wear underneath in cool weather
Now to my question...I was looking in 1861 petersons and I came across a picture that said it was called leggins.it was on a page with other little boys clothes. Can anyone tell me is this worn with short pants to cover the bottom portion of the leg? It looked like it buttoned up the side? Do you think it is made of wool? Thanks for the help!