Hi Kathy the entry in Tallanstown I would read as follows " Henry of John Reilly and Ally? Hamil and underneath the God parents are Thomas Conlon and Mary Brannen or Brennan more commonly.
The Kells Reilly is the one you asked about but wrong year, Henry is not a common Irish name and I am guessing it was not too common for the RC faith back then so two is unusual I think but my thoughts are not scientific. Wonder if the families are related, however Reilly is a common name associated with Cavan which is very close to both Kells and Tallanstown. It is unfortunate the priest did not record the townland the family were in.
The "O" was only used in about 4% of Irish names back then, increased after about 1880 with the land wars and the rise in nationalism. In fairness to the US and Canada most people arriving would be either illiterate or possibly speaking Gaelic so spelling was phonetic.
The Reilly / Phelan / Fallen, probably Fallon, do you really want a fallen woman in your ancestry!!!! Seriously if you can supply dates we can have a look up, also area or county.
If you are getting close to travelling you can mail me at my site email stpeters@irelandxo.com this will speed up the response rather than waiting for the notification which only comes in once a day.
I searched both the Tithe Applottments and Griffiths Valuation (are you familiar with them) for a Henry Reilly nationally, I got 7 in the Tithes, nearest in 1826 on the Cavan/Meath border slightly nearer to Tallonstown but not in either parish, more interestingly there are only 7 in Griffiths and one in 1854 in Maudlin Street, Townparks, Kells, and I imagine this may be your Kells family if that turned out to be the correct one, from the site you can probably pick out the place as the griffiths site comes with a map, remember though this is an opinion based on the Henry christian name being a family name and from the few of them there are nationally. If you wan the site for Griffiths it is here http://www.askaboutireland.ie/griffith-valuation/ various icons to the right give extra info, take site number from the 1st icon when you open it and then search the map, not the easiest thing to do but Maudlin Street is still there, am not sure it would have changed hugely but buildings would be more modern.
Enjoy the journey,
Pat