The Griffith Valuation of 1855 has 9 Kilderry's listed
none named Peter so have probably already left. None from the same Parish as the Ready's.
At least he should have a name easy to find, as both first and last names are unusual.
Catholic families needed to baptise children very quickly as compared to Church of Ireland/Methodist etc. So if Nora went home to mother for her delivery her son would of been possibly there. No hospital deliveries in those days. Perhaps she was visiting Scotland or possibly you have a couple of Michael's mixed up? Families in those days would take on other families children either out of financial necessity or perhaps for school.
If her son was Michael Ready then that should be her maiden name or possibily a first husband's. I would imagine
Michael Rudy would be from the first marriage as there is 8 years between him and his sister Ellen. She could of been married more than once!
I'll come back as I need to take grandchildren to school.