I was in area couple of times last year and played almost all of the courses mentioned. Driving is not quick but the scenary is wonderful. Use the ferry across the River Foyle.
I suggest a 3 base trip - 1 base to cover the Portrush/Castlerock/Portstewart area. Another to cover Ballyliffin/North West GC and another base to cover the central/southern part of Donegal.
Not sure of accommodation for the P/C/P area but The Strand at Ballyliffin is fine and Dunfanaghy (B&B/Arnolds Hotel?) would be a good base - as from Dunf' you can cover N&P (1 hr), Cruit and Gweedore (40 mins), Dunf' itself, Rosapenna (20 mins) and Portsalon and Otway (35 mins) from there.
As to the golf, well the bigger names speak for themselves, Cruit Island shouldn't be missed and Dunfanaghy is joyous and underated.
I'm pretty sure you'll enjoy all the courses - if you have the time, take the opportunity to play some of the less known ones as warm-ups to the main courses, ones like the epic Bann at Castlerock, or the par-3 course at Rathmore/Portrush, or the 9-holer at Buncrana. There's a crazy 12-holer at Rosapenna by the driving range with huge undulations that looks a hoot.
Have a great time and post some pix.
atb