It depends on what your interests are and how you and they will visit things. Some of the stuff nearby would likely mean they would go on their own.
If you like museums and southwest Native American art then I recommend the Herd Museum. There are two locations now. The downtown one has Barry Goldwater's Kachina Doll collection. The north location has different stuff
If you have a day then go up to Montezuma's Castle. (I'd say a half day but with the short days now you'd need to be there early to see it all by noon.) You could combine this with a loop to Sedona but that would make it a full day trip.
Frank Lloyd Wright's Taliesin West has tours.
At the south end of the Valley is the Casa Grande. I put this in the category of "stop if you're driving by but it's not worth a special trip from the north end of the city". (Unless you're really into ruins).
South to Tucson is the Saguaro National Monument.
Note on Tucson: If there has been any rain in the area (and it happens that time of year) then within a few days the desert between Phoenix and Tucson can open up with cactus and wild flowers EVERYWHERE. It's amazing when it happens.
If you can extend your trip then of course the Grand Canyon ought to be on your list. This is a full day trip though - leave in the PM, stay in the area, do the South Rim tour during the day and then stay again. It's roughly 4 hours 1 way from Phoenix.
Already mentioned was the Sedona scenic drive. Another one is northeast through the Salt River Canyon. Both are full day trips with the short days this time of year.
Southeast out through Apache Junction to Globe is also a very pretty drive.
Southeast of Tucson are places like Tombstone (OK Corral is a tourist trap) and Bisbee (a beautiful little town set in the mountains at the location of the Lavender Pit open copper mine.) Again, these are full day trips.
All are mountain roads with lots of twisty turny (and sometimes, 1000' drop offs) roads. They would be great in a GT
Maybe take a few days and send them off sight seeing and take a Bondurant class yourself.
P.S. Going to Phoenix in February will make you a potential snowbird. We desert rats recognize that the time from Sept. through May is our best season and that our summer (with 100++ temps) is your winter.