First World bike choice problem

So, off to Scotland next weekend for two weeks; a week on the mainland based near Poolewe and a week in the southern Hebrides (Uists etc) not Harris/Lewis. Primary purpose is sea kayaking but always have a Plan B when sea kayaking  in case it's too windy, so taking a bike. Gravel or MTB is the choice. I know a few mountain bike routes around Poolewe but out on the Isles nothing I'm aware of.

So, anyone with better knowledge of the areas have any advice which might sway my mind? And I really don't want to take both bikes...