Short time but ...
Start with Carrowkeel. Heapstown cairn. Moytira East court tomb. Carrickglass portal tomb. Then Magheraghanrush. That'll be day one. Maybe up to Creevykeel if you have time.
There's a good B&B on the side of Knocknarea - Primrose Hill Farm. It's very near to the entrance
to the car park for going up Knocknarea. Up Knocknarea and then go to Carrowmore on day 2 (main area shut at this time of year - up to you if you go in anyway). Tawnatruffaun is a must see and Crowagh portal tomb on the way across, but these may be out of the way and better saved for a trip to the Sligo/Mayo border area.
Cabragh wedge tomb is quite nice, but very out of the way.