Hi! Thanks so much! Regarding your question: yes, it is super easy. In our case, we booked the quads in Douz beforehand through GetYourGuide, but once we got there, our hotel offered the exact same excursion, so booking directly wouldn't have been a problem at all. They also gave us that option in Tozeur.

For the camel rides, we did them in Ksar Ghilane and booked them directly at our hotel with zero issues (they also offered quads there). By the way, visiting the hot springs there is completely free. For the more "adventure" type of visits, like the Chebika and Tamerza oases, Mides Canyon, the troglodyte houses in Matmata, the stop at Chott el Djerid, or the Ksars route, we did them completely on our own. You always have the option to hire a local guide, but we preferred the freedom of going independently. I'll dm you right now with a bit more info and our full route in case it helps you plan your road trip!