Hi;
Try to pre-book your Excursions in Advance before arriving Marrakech, sometimes you can leave it as a last minute during the low season with no problems as you will find the best with all suits your pocket and your interests.
Use the Things to do Tab for Tours, for every location example Marrakech here, or the The Top asked Question on the right side of this forum Tour companies, and for Drivers you can use the Search box for shared information about reliable and trusted Drivers.
so when you have no idea you can ask your riad to Manage it for you through a Local Tour company.
I agree with MIB15 in advice for the Quad Biking to be done in Essaouira as the best location to enjoy it by the coast line, as you can do it in Marrakech too at the palmerie, for the Best Day Trips to make from Marrakech would highly recommend High atlas Mountains to Imlil, and take a look at Toubkal Kasbah, read helpful threads using the search box for previous Topics about anything concerning your travel needs.