I don't know where you're staying that evening, but in addition to the courses mentioned you could consider Dingle GC (a bit over a 90 minute drive from Ballybunion) or Killarney-Killeen (60-minute drive from Ballybunion). Dingle (Ceann Sibéal) is a very natural, low-key course that doesn't get as much American-tourist traffic as Tralee, Lahinch, and Doonbeg. The ninth hole plays as one of the longest par fours I've ever experienced (uphill and into the prevailing wind). Killarney-Killeen is a fine test of golf in a beautiful setting (though I don't really care for Killarney town -- too crowded). Both of these courses have been worked on by Eddie Hackett.
Also, you should really seriously consider playing Lahinch Old or Doonbeg twice. We Americans (and I'm guilty of this too) seem to descend on Ireland and knock off the courses like some sort of conquest. When each day brings a new course, it's hard to truly appreciate its design when your only view of each hole is your singular path that day. Only by playing a course in multiple conditions and from the variety of distances and angles that come with each new round can you truly come to know it.
I'm a member at Doonbeg and this past September I played 10 rounds there over a period of two weeks (the other time was spent up in the northwest). My golf game, the weather conditions, and my experience of the course was different each time. Still, I only feel like I'm just getting to know and appreciate all of its subtle (and not so subtle!) aspects.