Sorry for the slightly annoying advice, but what i saw of the roads in Mull would have me taking a road bike over a mountainbike any day! All sorts of daft switchbacks/corners/gradients...
We did see a little woodland walk beside Calgary bay, which i walked around grasping my virtual handlebars, nice wee trails but a bit 'cheeky'.
The map showed a trail north of Calgary bay that took you to one of the northern points of the Island, where reportedly the resident sea eagles have been seen taking Fulmar, could be an interesting wee expedition?