In reply to Gazlynn:
I know Dalmellington very well, I only lived about 7 miles from it. It's on the Ayrshire side of the hills, and together with Patna is a mining town and not somewhere that folk usually choose to holiday! Not really in the Forest Park to my mind either.
The Airie house probably isn't ideal in this case. It depends how far away you want to be. New Galloway or Dalry are c. 30- 40mins drive from Dalmellington, on the N end of Loch Ken. There is a watersports centre, good walking etc. In between N.G. and Dalmellington are the Southern uplands, so proper hillwalking round Carsphairn area (and not much else). Solway coast down to Sandyhills or Kippford is a reasonable day trip from there, and towns like Kirkcudbright and Castle Douglas are pretty enough for a spot of interest.
The other option is to go into Ayrshire, the Culzean coast, or the area round Mauchline are nice but check driving times. These I don't know so well.
Good luck!