Nauvoo is an awesome place to go.
The people are friendly.
Get there early to get tickets for the Horse drawn or Oxen drawn narrated rides that give the history of Nauvoo.
Great time and awe inspiring place.
Was there in 2001 for the open house and then back for the deadication of the temple there. Really cool history and things to see there. Best buffalo chickens wings in the world just up the river from there, don't recall the town's name but I was told by the owner that Harrison Ford would fly in just for those buffalo wings.
Hit Carthage too if you have the time.
The Mormons are good folks and most are very nice and not over bearing with the religious stuff.
Great time of year to be up there too, enjoy!