Tom,
There are numerous other threads on the topic if you use the search function. We typically alternate 36 and 18 hole days. Now I'd probably try to tack on an afternoon on the par 3 course or the putting course on the 18 hole days. Depending on your age and fitness level, some guys try to do 36 and even 54 a day. It's all personal preference as to the courses, IMO Bandon Dunes is somewhat overrated due to it being first and historically important, but you should certainly play it once if this is your first trip. If I had 8 rounds, I'd go 3 OM, 3 PD and 2 BT, but this will vary greatly by poster. If you're a strong player you may like BD and BT more than if you're a higher handicap. BT is nice to schedule for afternoon rounds when the wind can be pretty brutal along the ocean, particularly in summer. I'd make the connection into North Bend via Portland or San Fran. Might want to consider booking a massage mid trip. Finally, enjoy!