Dinning Family Northern Ireland C 1840 S

I am looking for the forebears of John Dinning probably born c. 1820's who married Hannah Thomas in Northern Ireland. They lived in Garvargh. She was a corn merchant's daughter, and John also became a corn merchant along with general farming. They had several children, most of whom dispersed to either Australia or the U.S.
John Hunter Dinning, b. 1844 Garvagh, is my g.grandfather and had several siblings - four emigrated to Australia, and some - perhaps three emigrated to the U.S. It has recently been found out that the mother, Hannah nee Thomas, went to the U.S. in her later years to stay with a daughter, and died there. There is a record of a John Dinning falling a stream and dying, in/near Garvagh, at a relatively young age, so if this was the above John Dinning, she would have been widowed young.
The children who emigrated to Australia were: William Dinning, the first of John and Hannah's children, and first to emigrate to Australia. He was born in 1842 and emigrated c.1859.
Second born was the above mentioned John Hunter Dinning, arrived in Australia in 1861.
Third born was Henry Wallace Dinning, b. 1846 and emigrated May 1867.
Mary Dinning was the fourth child of John and Hannah, and was born in 1847. She emigrated to Australia as a cabin passenger on the SS Great Britain in 1866. She married Robert Graham in Australia.
The last of the siblings to arrive was Edward Thomas Dinning, born it is thought in 1851. He had a mental handicap.
We do not know anything about the births of the other siblings - at least one stayed in Ireland; the rest went to the U.S.. The ones emigrating to Australia were met by an uncle Samuel Dinning. He was born in 1797 in County Derry. He was convicted in Ireland for stealing an iron staple and transported to Australia for 7 years. He left behind a wife and 3 sons and a daughter, of whom we do not know any details.
If anyone thinks they might have the family tree details of John Dinning senior I would be very pleased to hear from you.