On the 1851 Census - transcribed as Whealty.
Robert, 43, b. Ireland; Mary Ann 35, b. America
Robert, son, age 8, Scholar, born Malta
Siblings - William 15, b. America; Agnes 13, b. England; Mary Ann 10, b. England; Elizabeth 4, b. at sea; George 1, b. St P. Port
As you say, address 46 High St.
Last sighting for Mary Ann, born 1816/17 is as an outpatient of St Peter Port Poor Law Board, May/June 1879, address 27 Park St. She's not at this address in '81. I think I see Emily in '81 but Annie is so, so elusive!
PS - have spotted the Welsh connection.