Kavanagh/Landy

I am descended from Patrick C/KAVANAGH (abt. 1783-1868) and Mary LANDY (abt. 1787-?). They were Catholic.

I have found the baptisms of their first 6 children in the Catholic Parish records in the Roscrea Parish. My understanding is that this religious parish overlaps into the counties of Offlay and Laois. 

Their children and year of baptism:

John 1813

James 1815

Patrick 1817

Denis 1819

Peter 1821

Mary 1823

Their next 3 children were born in Quebec, Canada, where they immigrated between 1823 and 1828.

Margaret (my direct ancestor) 1828

Michael 1830

William 1833

Of the 6 children baptised in Ireland, these were the sponsors who shared their surnames: John Cavanagh, Honora Cavanagh, Dan Cavanagh and Nelly Cavanagh. Also James Landy and Margaret Landy. My understanding is these could be siblings of Patrick and Mary. 

A "Patt" and Honoria Cavanagh were sponsors for Mary Kavanagh, dtr of John in 1817. 

There other Cavanagh baptisms in that parish and less Landys.  I don't see a marriage for Patrick and Mary, even though marriages seem to go back to 1810.

I have a note of a Patt Cavanagh in the 1828 Tithe Applotments in Kilmore, but they were likely gone by this point.

How else can I get an idea of where Patrick and Mary might have lived and who their families were? Also, were there ever any burial records? I don't see that all of their children made it to Canda, specifically John, Denis and Peter. They were young enough that I would have expected them to not stay behind, so maybe they died before then?

Thank you,

Mary