Hi Rich,
Findhorn Valley for red deer and juvvy eagles, though any valley will work for deer. By pure coincidence, the car park at the end of FV is the best place to look/listen for both so you can in all honesty say that you taking everyone to a good place for deer and conveniently forget to mention the birds <big grin>
Gairloch's along way and the boat is the sort that might encourage a bit of impromptu chumming if you get my drift. Note well, make sure you sit up wind...
Would still opt for the Ullapool - Stornaway ferry as foot passengers. Boat is much more stable with restaurants bar on board. Last time we did it autumn, we had hundreds of dolphins and porpoises, minkes, plus seabirds. Being that much higher, you get better views of the scenery (stunning) than you do on the inflatables plus the chance to look down on the wildlife. The height also gives you a chance to scan greater distances, increasing your chances of picking things up in the first place. And a lot cheaper too.
Have a great trip wherever you end up.
Cheers,
Gordon