If I may, I'd like to suggest a day out north of Inverness to the bit beyond the Black Isle.
1. Tarbat Ness Lighthouse
2. Walk along the beach at Portmahomack
3. Visit Glenmorangie Distillery, because Dalmore Distillery is currently closed.
4. Have lunch in Tain. Either Harry Gow for a Scotch Pie and a Dream Ring, or across the road if you want posher/warmer.
5. Walk from Contullich up Fyrish to the Monument. Not for the monument but for the view across Cromarty Firth
Actually, go anywhere, do anything. Whatever you do, enjoy it, that's a fantastic part of the country to be in.
Edit to add: If you fancy a day of spectacular driving you could do a lot worse than head across to Ullapool then down the coast road to Gairloch (taking in the Russian Arctic Convoy Museum at Lock Ewe, obvs.) then head back via Kinlochewe and Achnasheen and Garve.