I'm in Sundance, been here since May, and I think it's great!
It can be a little tight finding housing, especially with a family, but it's not insurmountable.
I've met a lot of friendly people in town and have some regular friends now.
For shopping I typically head to Spearfish SD a half hour away. There's a grocery store in town that I go to for convenience but I try to combine the drive to SD with a restaurant trip or a movie or something.
The football team won state last year (not sure what division).
I like it because even though it's a small town (~1200 '00 census, but there's more now) it feels a bit bigger I think due to I-90 and proximity to Spearfish.
Even Gillette is only an hour away and they've got more services and Home Depot and stuff.
Can you move your business with you? For "good" jobs you'll probably have to go to Gillette, Newcastle, or Spearfish, but depending on the age of your kids the local places are all hiring now that school's back in session (gas stations, restaurants, etc.).