I did a similar 4 day trip back end of August only i was solo and camping. Did a couple of nights at Durness: the road from Ullapool to Durness is stunning as is the road across the top to the East coast.
I must look out for that cafe at Lochcarron as i seem to have missed that on my trips. Hope they do lots of toast to go with that brekkie just to pack it out a bit