Stayed at Shannon Oaks last year and wasn't very impressed.
Was in Mount Wolseley about 3 years ago and that was nice, they have 4 bedroom houses sleeping 7 (a double, 2 twins & a single room).
I just had a look at Dream Ireland's website - I have used them a few times and generally been happy - and came across this place - holiday homes at the Abbey Court Hotel, Nenagh. I know nothing about the hotel but what caught my attention was that there are 12 x 5 bedroom houses and 2 x 8 bedroom houses. Rates seem to be a little over €1,000 for a week, which seems like a good deal for houses that can accommodate so many people and claim to be 4* standard.