Clarion Liffey Valley is fine. Nice Asian Restaurant too. I found it a little noisy though - more so because we had a baby with us.
I suggest Hilton Dublin Airport. Ironically, it is 3 or 4 miles from the Airport. It is located on the Malahide Road oppsite Clare Hall Shopping Centre. Rooms can be got for as little as €60 and they are beautiful. Find it on www.hilton.com
I have stayed at this hotel a few times despite the fact that I am traveling from west of Ireland. It quite accessible from the M50
Be forewarned, even though the rooms are cheap and the breakfast is good the drinks in the bar are very expensive and they charge crazy money for WiFi ( I think it was €20!!!!!!!!!!!!!!). Room service can cost more than the room. Run across the road to the 24 hour Tesco for a sambo and a beer. There is n oriental a restaurant next door which I haven't tried yet.
I'd recommend hotels on the Luas or Dart lines. Red Cow Morans Hotel and The Beacon or Bewleys Hotel all have ample parking and are close to Luas Stations for travelling to the CCentre. All nice hotels. I work in Sandyford and Bewleys are advertising rooms from €58 per night. Nice clean modern hotel. Not too sure of hotels on the Dart line - Stayed in the Tara Towers in Booterstown last year, it was very reasonable and clean and located 2mins walk to Booterstown Dart Station
Have stayed in the Louis Fitzgerald, very good and not bad rate. Plenty of parking and a courtesy bus to Luas and back at certain times. Not unreasonable times either. Give a ring to check the times, but well worth looking and you dont have to drive near the city.