Great finds!
I had wondered why William Reader wasn't present in census but I suppose being a boatman meant he travelled around a lot. There was a William Reader in Warwickshire who was imprisoned and transported in 1838. He was listed as having 4 children, but after doing some digging it was clear that this person's occupation was listed as 'ribbon weaver', not a boatman.
If William Reader went on to marry a Sarah and had a child called Sarah Ann then this would create a possible link to the Sarah Ann witnessing my Mary Ann's marriage.
Looking at the 1841 census, I know that Mary would have been registered as mother's maiden name Wassell. I found her birth registration in 1838, and her mother Amelia Wassell died in 1839.
It looks like you've found the birth for Sarah, but Emma doesn't appear to have been registered. There is an Emma Reader who died aged 1 in Stourbridge in 1842 who might fit.
In 1851, I can't seem to find a birth record for Ellen Jane.
