My name is Clare Horgan I am a volunteer for the Claregalway area in Co. Galway.
I did a little research on resources available to me. I hope some of it is helpful to you in your search for grandparents.
I first went to see if Thomas and Bridget were married in the 1911 census. No Luck. http://www.census.nationalarchives.ie/search/
I did find a Thomas Dillion in 1911 (25 years) matching your description on that census
Information on the townland they lived on. He might be yours
Looking for a civil marriage cert for Thomas Dillion/Dillon and Bridget (nee Dilion?) which have marriage certs available up till 1943 online on www.irishgenealogy.ie (free access). I could not find them there.
I also could not find a Thomas Dillion marrying a Bridget at all in the Civil Registration District/Office Mountbellew area on www.findmypast.ie (subscription access).
Do you have any more information, dates? Names etc.?
Due to the 100-year rule here in Ireland on birth civil birth certs, I can not find any of their children birth certs online. The GRO in Dublin will have physical copies to view at a charge.
You may have to go down the root of a professional genealogist who can do more detailed research for you. Let me know if you need any help with finding someone.
If you wish to contact me for any help and guidance, I would be only delighted to help.
My email is email@example.com
Best of luck