Hi
I don't think the overseers would count older children who weren't still dependent on their father. So you need four younger ones. There is no W for wife, so Jno in that record was probably widowed.
Mary born 1809 married George Deacon, and links to the younger Ann via the 1851 census.
Getting a look at William's marriage and comparing the signature of witness Ann to the one who married in London might be useful (well, it wouldn't do any harm!)
Jon