Don't worry, they dressed about like anyone else, but were a bit more dirty. The daughter would be right in a prarie dress, be careful around the fire though.
If you want some just blacksmith clothes, since they will get dirty, I'd just buy a pair of blue denium bibs and remove the front pocket and the hammer loop before wearing them. Most bib of the period lacked both. Get them plenty big, folks wore them big. Go to a thrift shop and buy a couple three cotton flannel shirts in the red or brown plaids. Don't worry if the fronts button all the way down, some shirts did and with the bibs no one will notice anyway.
Also go to this site:http://memory.loc.gov/ammem/award98/nbhihtml/pshome.html
Type blacksmith into the search and enlage them. I know ith out looking there are several pictures, also type in livery stables and see what you can see.