We were at Eglish several years ago, but were unable to meet with the priest. We did find some parish records on microfilm at the National Library in Dublin - might be worth a look if you're ever there. There is also an Eglish Parish census from 1840 at the National Library, which had lots of Kellys. We only made note of the Michaels, so your Kellys might be listed.
There are Kellys in the 1854 Griffiths valuation, Town of Birr, and I see at least one William Kelly listed in the 1827 Tithe Applotment Book of 1827 for Eglish Parish. Have you seen these?
Writing to Eglish Parish has been on my list of things to do for a long time - I really need to do this!