Walsh Offaly 1800s
You will probably need (an idea of) a Parish or Town or townland in Offaly. I have just had a quick look at Griffiths Valuation for the 1850s and there are a lot of Walsh families tenants or owners at that time. If the husband and wife you mention left any family behind they will probably appear in the 1901 census which is available on line as is Griffiths Valuation. The former is indexed and by going through all the occurences of Walsh in the census you could find similar children names as your own family specially in the early generations. Also try Walshe and Welsh as this latter is frequently the Offaly pronunciation!
Hope this is of help to you. I am an amateur searching for an old root