Cathy,
It wouldn't be particularly easy or comfortable as it would involve both a sea journey and a road trip.
There were several possible routes that they could have taken to Carradale.
a) Via the Sound of Mull to Oban, and then a long trek through mid-Argyll to Tarbert and from there down the west coast of Kintyre to their destination.
b) A journey down through the Sound of Islay and across to West Loch Tarbert, thence by road as above.
c) By ship via the Mull of Kintyre and north to Carradale. No log trek by road. Depending on the time of year and the weather, this could be a less than smooth journey.
d) Via the Ross of Mull and past the north of Jura, through the Gulf of Corryvreckan and then along the Crinan Canal to Ardrishaig, again with a fair trek ahead of them via Tarbert. This route would depend on the size of ship to enable passage through the locks on the canal.
I'm sure that there were several other routes that would have been available to the travellers. If you have a look at Google maps satellite view you will get some idea as to what was involved, and why sea and ferry travel on Scotland's west coast was important up until the mid/late 1800's at which time better roads were being constructed.
You may find the following site of interest
https://www.aniodhlann.org.uk/?s=kenvarIstrice