EGCJ flyer,
I'm not a fixed wing pilot, but can I suggest that you book a trip with an instructor to get some practice some short field stuff at MATW? Having said that, it sounds as if you are the sort of person who would have worked that one out for yourself. Your idea to ferry your pax in from Oban is a good one.
I can see that some of the posts here could be seen as being negative, but I am sure that the posters dont intend to be. What they are trying to do is impress the importance of airmanship on you and that is no bad thing. You have to go out there and try these things for yourself, but make sure that you are properly prepared (remember the 6 Ps). I personnally wish I had been more adventurous when I was hour building (from Sherburn as it happens).
I think the weather will be the main player in your trip. The weather in Yorkshire is usually very different from Scotland. In fact the weather can change dramatically from one part of the West Coast to another. So far the Scottish summer has been notable by its absence. If I was you, plan the Mull trip, but have a plan b ready if the West Coast is wxed out. Above all enjoy yourself and fly safe.