Christmas Plans

As mentioned on a previous post, my twin brother-in-laws, Don and Dan are flying over for Christmas vacation. Hopefully, their plans remain solid and they'll be able to bring L's niece and goddaughter Katie. This will be the first visit here in Utah for Don and Kate, Dan having been here once before some years back.
The whole fam is buzzing with excitement. It's not everyday we get family to come visit aside from my sister. The twins are a year older than I am, but I swear they'll be 21 forever, which of course makes them loads of fun. I may not remember all details and subjects of our conversations, but I sure recall that I am laughing the whole time. And our niece is a senior in high school, a lovely young lady already, who is adventurous and ready for fun.
I would hate for them to come all the way here and just veg out on the sofa in front of the tv, so L and I have been scouring the internet trying to find fun activities to ensure Fam Och (Utah version) is the coolest destination to visit in the hopes of repeat trips back here.
So far, this is what we have:
Visit to the Salt Lake Temple.
-the timing is perfect, with the lights on at this time of year, and hopefully we can fit in a sleigh ride for the kids with it
Speed Raceway
-L wants to race the twins, and I'm thinking Kate would love to drive, too
Salomon Center
-L and D have been dying to get a second trip in the iFly tunnel and hopefully the rest of the gang would try also
-iRock, bowling, and glow golf sounds like fun, too
Gorgoza Park
-since Dan won't be able to ski/board b/c of a bum ankle, we figured we'd take the whole fam tubing

As I sat clicking away on this laptop, it dawned on me that asking you locals would be better! So don't let me down, neighbors!

Please suggest away! Activities, destinations, dining locales, anything to make this trip memorable for them!