I'll have 4 full days. Any suggestions for hidden gems? How about afternoon excursions? Any tours you'd recommend?
We had amazing meshaoui (steamed lamb) in a little alley off the big square. There's an article about it here:
https://www.vice.com/en_us/article/vvqjy4/walk-down-marrakechs-mechoui-alley-for-the-best-roasted-lamb-of-your-life
We visited the main sites (palaces, saadian tombs, etc) and enjoyed them all. Le Jardin Secret was also a lovely, peaceful place to visit.
We paid for a 3 hour walking tour, but didn't think it was anything special. The guide took us to all the places we were planning to go to anyway. We did visit the photography museum, and found that to be quite interesting. We did not visit anyplace outside of the old city. Enjoy your trip!
You can do a day trip to essaouira - it's a beautifuil medina by the sea.
I'm thinking Essaouira would make for a pretty long day trip. I liked Essaouira (was there long ago), it makes a refreshing break (with much-appreciated, cooling sea breezes) but I'd give it at least an overnight.