Seeking Unique Things to Do with Out of Town Company

I think you've covered the gamut except for maybe Southfork Ranch. I would like to recommend that you not visit the World Aquarium at opening time, but in the middle of the afternoon. Pair the Aquarium with the JFK memorial and museum, then go to El Fenix - you don't get much more Dallas than that for Tex-Mex food. I don't know if Six Flags is open during the winter; that might be too cold. I think it's important to have down time at home, too. Bass Pro Shops in Rockwall is nice, and there are several restaurants next to it.

I have not been, but is the Latern Festival still running at Fair Park?
The Perot Museum of Nature and Science has just opened north of downtown.

I was going to recommend the Perot museum. I have some guests coming and planning to take them there. :-)

There are Segway tours of downtown Dallas I recommend. Also, a stop by the historic Neiman Marcus in downtown along with reunion tower outlook deck would be nice.

You have come up with some good ideas yourself!!

Depending on scheduling and $$ a trip to the Mavericks game?
Fort Worth Stockyards
South Fork Ranch is not that far away of they were Dallas fans
Northpark Mall is a classic
The Ice at the Gaylord in Grapevine
Go to the top of Reunion Tower
Top Golf in Allen is a lot of fun
Drive on the high 5. It amazes me at how our guest have been so taken back by that drive. Of course, don't do it in peak traffic time!!

That said, I don't know ages of everyone and how many children are involved. I am sure they will appreciate any of the efforts you are making to show them a good time.