Art
You have to separate the northern (Outer) Hebrides from the Inner. The only way, for example, to get from Islay to Uist is via the mainland, either by flying back to Glasgow, or sailing back to Oban and picking up another ferry. To do a full golfing tour of the Hebrides (counting Kintyre as an island, which for these purposes it might as well be) would take quite a long time, and be a pretty gruelling itinerary. But you can do, say, Arran, Kintyre and Islay (and perhaps the nine-hole course on Gigha, which isn't anything special but is worth popping into if you're passing) quite happily in a week.
I spent a week at Machrihanish in May a few years ago; the weather was quite good (I still think May is consistently the best weather month in the west of Scotland), and the course was quiet. I liked the Dunes when I saw it in 2009, but one must accept that, given how it has been created, it is a work in progress and will continue to be so for some years. And its routing is compromised by the environmental restrictions, making it a pretty long walk.
I haven't played the Harris course, but have driven past, and it is a really beautiful spot when the weather is nice. The famous connection there is Nick Faldo, who stopped and played there while on holiday once. You paid your green fee into an honesty box, which he did, also leaving a note, so they now play for the Faldo Fiver as a trophy.
Of Askernish I have written much; suffice to say I really believe it is a place every golfer should see if he can, and I honestly think that with time it will come to be regarded as a world-class golf course.
There is a ferry linking North Uist and Harris, so you can drive the length of the Outer Isles if you wish. The eastern side of Harris has to be seen to be believed - it is so rocky as to be like a moonscape, and it is hard to comprehend how the islanders survived when they were forced to move off the fertile machair on the west of the island in the nineteenth century, to make way for sheep (and very easy to understand why so many of them emigrated to Canada).
I love the Hebrides, and would happily spend a holiday pottering around, playing a few of rounds of golf in between hillwalking, visiting distilleries and the like. But it is a tougher agenda if golf is the be all and end all of your trip.