The 1881 census entry is quite clear and is as stated.
However I believe Isabella Caren's age is wrong and should be about 55.
The children are her grandchildren. Her daughter, another Isabella, married Johnn Roney 12 Feb 1863, see my marriage index.

The 1871 has:
Douglas, district 6, schedule 40, 1 Quayles Lane
John Roney, head, married, 29, boatman & pilot, Douglas
Isabella, wife, married, 27, Douglas
John, son, 10, scholar, Douglas
Isabella, daughter, 6, scholar, Douglas
Robert, son, 2, Douglas