The drive to Abha from Khamis Mushayt can be very interesting trip, but as usual drive carefully. The road from Sharourah via Najran is daunting, but interesting - up and down ribbon across the dunes, with an old version off to one side for may kms. There were Camel warning signs along it, but some were single hump silhouettes, others had 2 humps !
You can also drive in from the west coast , with lots of winding roads, bypassing old washed out bridges, lots of signs of floods, some picturesque villages etc, or from the north from Taif - lots more twisty roads, and not as interesting as going to the coast. Neither trip offers much in the way of accommodations, so be prepared to camp out.
lookout Mt Sooda. Trip to Habala Hanging Village - couple of hours. Trip to Turkish Fort - also couple of hours - fabulous views down a valley towards Yemen. Many older houses made of mud brick, with slates sticking out to fend off the water. Many nests in bushes of weaver birds. Most hotels will put on tours if enough people interested. One trip in August it actually hailed very hard!
Try driving down the road from near Jabal Sawda (its insane-see picture), almost as good 'Monkey Road' heading to Mohayil or the road to Taif over the mountain range all the way.
The cable car.Climb up Jabal Sawda. Try to visit the airbase.
Buy traditional Asir clothes for the children from the museum. And traditional 'silver' ware in the Khamis sook.