In reply to Flinticus:
Yes that's the right Arkle stream, the scrambling isn't anything special but it's a nice place and everything tricky is avoidable if the dog needs to.
Second Dionard is at 359 482. Assuming you come up Strath Dionard, pass under the obvious huge First Dionard Buttress above the head of the loch, ignore the right-slanting ramp just left of it (dead end) and take the next (bigger) ramp along, between two layers of vertical cliff. The edge of the ramp above the lower cliff is quartzite slabs, further in it's grassy. It takes you to a nice perch on the top of First Dionard, then outcrops and deer tracks lead up to the top and you can come back along the main ridge. It's a cracking day out (best part of 30km).
Ben Stack N Flank just go up the usual track to 350m, traverse left and pick outcrops as you fancy. The second vague buttress along is about the best. I've done it with a couple of friends, one a non-climber and he went round all the outcrops with no problem so the dog should be fine. You can make it any grade you want.