for reference here a link to the census return :
Galbally household, Oak Park - 1901and the family on the 1911 census :
Galbally household, Oak Park - 1911The 1911 census indicates that the couple are both from Co. Kildare as are married 13 years, so about 1898. I dont see any good matches on the BMD Index for a marriage of for a Michael Galbally, but there is a good match for the birth youngest son James :
Name: James Galbally
Registration district: Carlow
Event type: Birth
Quarter and year: Oct - Dec 1909
Volume : 3 / Page :302
A birth cert would give you Johanna's maiden name which would help the search for the marriage, and give you names of their fathers and other details which would help you search further.
Michael's birth is before the start of civil registration you would need to search for parish records for his baptism.
Shane
Note - 1911 census link fixed (was connecting to the 1901 page by mistake)