Went into the store to shop and the information desk personnel confirmed that overnight parking is allowed. They asked that we park on the north side which has several pull-through spots. I prefer to park in a regular spot and leave these for big rigs, but it was not very busy. Quiet location with some good shopping and restaurants.
Staying here in a Saturday night, the area was noisy for quite awhile (cars honking, boating music, revving engines) but did eventually quiet down after the restaurants closed for the night. Be aware of that if you're an early to bed family - but all in all, it's somewhere near Salt Lake City that allows free overnight parking (confirmed by a call to the store), a rare find! There is separate, signed parking to the side by the dump station. No fresh water fill up, though, just the paid dump station.
About 5 or so rv spots off to the side. Also a paid dump site. There are quite a few restaurants in the same area so we were able to walk to them. Someone set up their generator next to us in the rv spots and we got exhaust fumes from them so we moved to the front parking lot. Had no issues parking there overnight either.