Maybe you could take your moho over for the day and play it by ear. If you don’t find somewhere suitable then you could return and stop on the mainland. I don’t think cost of a vehicle crossing is that much , if you went as a foot passenger you wouldn’t get to see much.
Visited Isle of Gigha a few times when we kept our boat in Scotland, we used it as a stopover on our way up to Oban if we had gone round the Mull of kintyre, Instead of using the Crinnan canal, usually anchored in a nice bay on the east side of the island, the sea and beach were gorgeous and everyone was friendly when we went ashore. That was our motorboat moored on the right and my son in our tender that we used to explore ashore.
Many places in Scotland we visited put out community mooring boats for visiting boats to use, many are free, with just a few where you pay a small fee in the hope that you go ashore and spend a few pennies. We were heading to Northern Ireland on this trip.