You'll definitely be seeing some gorgeous parts of Scotland. The highlands and islands are the best part, IMO. I went through a vaguely similar route a couple decades ago (yeah, I'm that old), on summer quarter off from college. Stunning scenery, but be prepared for your share of rain.
If time is not of essence, you can probably do this very easily on your own via public transport. Ferries ply between the islands regularly, bus schedules are good, and even if you're stuck in a remote village for an extra day somewhere because of transportation service is spotty, who cares? The lonely and wild parts of Scotland are an alluring place to be. Of course, if you have only so much time, you may need to do something like this to make sure you get to see a good chunk of what interests you.
On to specifics:
-- Skye is great. The Quirang has great hiking, if they give you time, as do the Cuillen Hils.
-- The Standing Stones of Callanish is an amazing place. My two buddies and I rode bikes out to it from our B&B, and we pretty much had the place to ourselves.
--I'm jealous you'll get to the Orkneys, in my 5 weeks, I didn't have time! That just goes to show you how much there is to see in Scotland!
To sum it up, if you have more time, do this on your own. If you don't, enjoy! It'll be great...
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"Life is not measured in the number of breaths we take, but by the places that take our breath away..."