Hi Elizabeth
Unfortunately, neither set of parents names are listed on the marriage record, making it impossible to be 100% accurate that the Patrick you mention, the son of Patrick and Betty is the same Patrick who married Catherine in 1841 in Tynagh. Unfortunately as the marriage pre-dates the beginning of civil registration in 1864 there will be no Civil or State marriage record available to compare.
You will be left with trying to make an educated guess I'm afraid. The time period would suggest a man who married in his early 20s, a woman from his local parish and having children and staying in the parish. All of this would lead you to the believe this, on the balance of probability, this could be your Patrick. There are about 10 marriage records in Co. Galway for a Patrick Whelan between 1836 and 1846. The 1841 marriage you mention to Catherine is the only one in Tynagh and again this gives credence to your information, assuming that is, that Patrick married someone from his parish of Tynagh and not a girl from a neighbouring parish.
In relation to sponsors, usually they are sisters and brothers of the parents or very close friends of the family.
I would love to know more about your trip here next year. Can you contact me closer to the time at cdoyle@irelandxo.com and I will do my best to help you out.
I see there are only 12 Whelan entries on the Griffith's Valuation in Tynagh. You could, if that is part of your planned trip, make a visit to the Valuation Office in Dublin to see if you can learn any more about who held the lands after that time (1856) on the basis that those Whelans might be connected to your Patrick. You can read a little bit more about the process HERE
Best wishes
Clare Doyle
Genealogy Support