Hi Dianne,
Visiting Ireland during the festive period is a wonderful idea. Generally, businesses are closed on Christmas Day (most hotels do remain open); however, many do reopen on the 26th, such as bars, restaurants, and retail shops (as winter sales typically commence on this day).
So, choosing whether to visit the week prior to Christmas Day or the week after really just comes down to your personal preference. Visiting before Christmas allows you to
soak up the atmosphere before the 25th, while the week after is usually quite relaxed with New Year's Eve just around the corner.
Whichever you choose, I'm sure you'll have a wonderful trip.
Regards,
Eoin