Hi Karen,
My suggestion would be to make sure you're on firm ground before going back another generation. Can you add the marriage record you mentioned to George's profile? Any census records that would help support George's date of birth? Also, I think you must have the wrong mother attributed to George's son Charles -- Rachel would have been in her 60s.
Also one or more sources showing Charles is George's son would be a good idea.
If you're sure of all that, your best bet for finding info on Daniel and Mary would be the 1851 and 1861 censuses (for approx. date of birth, location of birth, and religion). You could also try Hastings County deed and probate records, and Upper Canada land petitions at LAC.
I'm not at all an expert on Irish records, but my general sense is it will be hopeless to find things there without more specifics on where and when to search (that are likely only to be found in Canadian records).