Hope you are lucky with the radio and the weather. In 2018 we travelled from Oban to Stornoway via Barra and the islands, going up hills when we we could. I was using 2m fm (max 5w with a dipole) and M0JLA was on HF and I took a few HF contacts when neccesary. I found it very difficult to get contacts on 2m fm but there is an amateur on N Uist (GM0HBF) who travels around for work and listens on 2m, also a few people on Skye and a couple of amateurs near Stornoway. At the weekend it is slightly easier and it helps if the hills are on the eastern side with good take-off.
We are soon (11 - 18 June) going to be travelling from Oban on to the Isle of Mull and I will be looking for 2m fm contacts if I can get up any of the hills (ankle/foot problems). I am sorry that we will be too early for you. After Mull we got east to near Pitlochry but leave there on the 27th - sorry. Best of luck
Viki M6BWA