You can always get the Luas from the city centre to Dundrum village and walk the rest. In this way you will have lots of hotels along the Luas route to choose from. It will take about half an hour to walk from Dundrum to Ballinteer.
You could try the www.thebeacon.com This is located in Sandyford. You can take shortcuts from this hotel through housing estates to Ballinteer if walking.