I did that trip 4 weeks ago
EGCJFlyer,
I'm a 250 hrs PPL who did the Islay, North Connell (Oban), Glenforsa trip about 4 weeks ago, in a 160hp Warrior.
I flew up from Blackbushe, and then based myself at Islay, simply because I have friends who run the best distillery on the Island there (PM me if you're interested).
Islay is closed, strictly, on Sats (after 1030 local) and Sundays. I made prior arrangements, and had private sole use of the airfield for the whole weekend; it was wonderful. However, you will probably need to land once before it closes to pay the fees and make the arrangements. Very friendly and helpful people both at the airfield and on the island. A very different world from the Berks that I'm familiar with! Islay is a substantial Island with a one or two hours flying to be had going around it.
I flew up Jura, across to Colonsay (tried to see the famous Whirpool at the head of the straights, but couldn't find it), to Iona and then to Mull and Glenforsa, with 3-up. I planned this so that fuel was low (well within safety limits) for Glenforsa (followed by a full refuel at Oban). Although the grass was wet, the field is much smoother than Rochester or Compton Abbas, and the ground (at that time) was firm. I'd definitely ring ahead to get the field conditions, wind being the most important. I was told I was lucky that day because all the three windsocks were pointing in the same direction! Even when quite calm, the wind can mess you about on the approach, so take care.
Then to Oban for fuel and shopping, then back to Islay alongside the famous "Paps of Jura" during a beautiful sunset over the Atlantic.
I enjoyed the whole trip and want to do it again, but I'd say, do all the calculations, include all the contingency factors and believe what the numbers say.
Based on my experience, my advice would be this:
VFR flying is a dream around the Islands because it's very easy to identify where you are. It's the weather that can create the stress, and if you've been flying for several hours this can be risky. The local weather can change very quickly. I took off from Islay one morning in clear skies, and had to turn back from the Mull of Kintyre because of low cloud and sea fog. So plan alternates, and be prepared to turn back, because it's not worth pushing on when you're in amongst 2000ft to 3000ft mountains, which is what most of the islands are really.
You'll have a memorable time, get your pax to take loads of photos and tell us how it went. (I've got a photo of Glenforsa on right base if you want to PM me)