I lived in the SLC area for a couple of years. We moved back to the NE 1.5 years ago for DH's work.
While many LDS folks are very nice, I found the Mormons in the SLC area to be more conservative than the Mormons I'd known growing up in WA state. Because there are so many LDS in SLC, some Mormons don't associate much with non-Mormons. I did make many good friends in the SLC area pretty easily, though.
Regarding the kids, your biggest problem may be the public school system. With so many families having lots of children and one breadwinner, there isn't a really great tax base in UT with the result that UT spends the least amount of money per child on public school of any state in the U.S.!
Another problem with the public schools is that some of the non-Mormon kids are ostracized by some of the Mormon kids. I don't think it's entirely intentional, but the kids all know each other from their ward (church) and will play with other Mormon kids, often excluding the few non-Mormon kids. My adult friends complained about their children not being invited to birthday parties when the 25 Mormon kids were invited, but not the two non-Mormons. Likewise with playdates, etc...
There are some half-way decent private schools in the area. That would have been the route we would have gone if we were still living in the SLC area when DS hits Kindergarten next year. Most of the private schools are non-Mormon church schools. The Catholic High School (can't remember the name) in SLC is supposed to be quite good.
One thing that SLC has going for it, is that the people there are very family-based. You'll find lots of parks, activities for kids, an adorable little zoo, a children's museum, and the like.
SLC is about a 10 hour drive from
Disneyland, if that makes any difference.