I'm confused by your post. You're looking for a John Quayle b abt 1821 in IOM, was Emma Cottam b 1818 also in IOM? Cottam isn't a Manx surname, maybe England?
You say their first child was b in USA but then they were in England for the 1871 census?
Perhaps it would help to know the names of the children.
What in-laws were with them in 1871.
There are a number of John Quayles b abt 1821.