You could look at this. https://www.faredetective.com/farehi..._City-SLC.html

I flew from ALB to SLC on Monday 12/19/16 and returned on Fri 12/23/16 and booked with points. The flight out was just under 8000 points (Maybe $140ish cash) and the flight back was just over 20,000 points (Prob in the area of $300 cash). These were booked on 12/11/16 due to a last minute change in plans. In Sept I had originally booked BUF>SLC>BUF going out on 12/19 and returning on 12/24. Those flights were just over 27,000 points roundtrip. Obviously completely different departure city, but at least gives you and idea. Based on your statement that it's a family trip I would guess your traveling that following week which I would guess would be pretty pricey based on demand.

Regardless of what flight options you choose, I would also suggest nailing down a rental car asap and keep checking pricing. I used a corporate code that allows personal use and ended up with a Traverse for $268+tax for a grand total of $364(various taxes are over 20%). That was a good deal compared to other prices I was seeing.