On their way to Ireland!

It occurred to me that since we know Michael Mulcahy took, at the very least, his sons Matthew and Joseph to Ireland in 1905 - because we know they came back from Ireland - we know, well, that they went to Ireland. I hopped on Ancestry.com and looked at their database of UK Arrival Lists. This record, while not matching the Mulcahys exactly - it claims, for example, that they're all British subjects (Irish) rather than American, while their return records call them all US citizens - it's close enough that I think it's them. An M. Mulcahy, with 2 children, M. Mulcahy and J. Mulcahy, arrived in Ireland about a month before they left Ireland. (Good length for a trip.) This eliminates a few things I had thought unlikely but possibly:

• The rest of the family did not go to Ireland. I thought it possible that Mary and the rest of the kids might have come and just left earlier or later, but this appears not to be the case.
• The trip to Ireland is not the reason the Mulcahys aren't listed at 85 Luqueer St. in 1900. I thought it possible - but again, unlikely - that maybe this trip to Ireland had been a long trip to Ireland, 1900-1905. Again, not the case. Where were they in 1900?

M(ichael) is listed as a laborer.