Sounds like a great plan, just some suggestions;
-Keep at toll roads if there's any, libre roads are extremely slow, narrow, potholes, high traffic (slow and tedious to overpass trucks), speed bumps in every town, and there are no reliable services and sometimes dangerous spots for travelers. At toll roads, there are safer services such convenience stores and restrooms at toll booth area, you can speed up to 75-80 mhp, free mechanical service (angeles verdes), even your government travel security advisor suggest using toll roads. The suggested toll routes are MX49D and MX40D.
-Keep at safe or well-known hotels (chain hotels), in Mexico popular hotel chains are City Express, Hotel One, Fiesta Americana, Best Western, Holiday Inn, Fiesta Inn, Hampton Inn, Hilton and others. City Express and Hotel One are best in my opinion since they have small clean rooms for a great price (about 40-50 USD night), usually located only at main cities, in your case near your route there are such hotels only in cities like Torreón, Durango, Mazatlán, Chihuahua city and Saltillo. In smaller tourist towns like Cuatro Cienegas there are small hotels (not chain hotels) suitable for families. Never go or stay to roadside "motels", unlike the US, most of those places only allow up to 8 hours (some 6 hours), due those places are used for prostitution.
Sometimes you will require detouring to visit certain places like natural area destinations, usually, there are towns serving for that propose and there should be problem to detour to such areas I'm going to list;
-Poza Azul (26.922941, -102.123274), right next to MX30 near Cuatro Cienegas, it's a natural ponds area, with turquoise waters, resembles Yellowstone pristine pool.
-City Express Torreon, stay here for a night, there's a mall next to this hotel where you can find almost any store like in US (25.583382, -103.406803), at the mall I recommend Sushi-itto, its a japanese restaurant located at the first floor.
There's not really much to see in Mapimí town, just an old desert theme town, but has two main attractions wich will require to spend around 8 hours on both areas;
-Puente de Ojuela (25.793049, -103.791066), this might be one of the funniest gravel roads to travel on the continent, this road it's very scenic and scary to drive, you'll love it, for access it theres an operator that guides you if its safe to pass, due its a one lane road, so you must wait for the incoming traffic to pass (like 30 mins or so), as for the bridge it's just an historical wooden bridge with an old mine which you can be tour guided.
-Grutas del Rosario (25.668378, -103.877110), to access this remote area you most use dirt road for 20 miles, this area its under upgrade for paved road, so you should see half of your route recently paved, don't worry about security, its a safe place designed for tourists (not many visit it) but its a must go gem, this cave offers spectacular rock formations, crystals, this is a dangerous cave to travel due its poorly maintained by a wooded cable bridge, but youl'' be tour guided (maybe by a kid as my case xD) and it will make it as a great aventure like Indiana Jones..
Once you visited both places, use toll highway to Durango and stay at city express of that city (24.053279, -104.617638) (it's 2 hours from Torreón to Durango using toll, by libre that's up to 5-6 hours).
In Durango, just visit historic downtown (24.024532, -104.670495) and old west theme villa located here; (24.109463, -104.699075), if you like pine forest or parks, you can visit Mexiquillo (midway of Durango-Mazatlán; here 23.714841, -105.669842), there are cabins, waterfalls, canyon views, even tunnels in a bike area. For eat; try this awesome sandwich (tortas) in Wallander (24.027444, -104.674462), The Wafle King for breaksfast (24.023916, -104.679874), here truly mexican tacos, Los Corrales (24.024504, -104.679520), Kanin Ice Cream best in town here; (24.024739, -104.680169) and least my favorite pizza of all time (MUST GO IN PIZZAS IMO) Pizzas Pizzaly (24.036545, -104.634747), there are different locations in the city.
In Mazatlan there are many places to go, best one is the waterpark Mazagua here; 23.302543, -106.481745 and the Aquarium (23.229197, -106.427485), for eat, there are 3 must go places; La Costa Marinera (Seafood; 23.260903, -106.465740), El Panama (international food great for breakfast; 23.243698, -106.451192) and nationwide well known restaurant; El Chucupetas; seafood 23.186979, -106.218594 in Villa Union.
edit; watch for weather, in Torreón and surroundings (including Mapimi) is extremely hot and dry, like Vegas, over 90-100 F almost all year round except winter. Durango city is colder but still hot, around 70-80 F, at the Sierra its all-time cold (around 50F), with snowfalls at any time even in summer, during the fall lots rain will be present, Mazatlan is tropically hot and sometimes dry around 80-90 F. The Durango-Mazatlan highway can be closed if there's present even little snow or ice in pavement, that's for security means.
