I lived in the city of Davenport, Iowa which is not too far from Dubuque, and have made numerous visits to the area for family get togethers and other occasions. While there are not too many exciting attractions in Dubuque that will keep thrill-seekers entertained, for a city in Iowa it actually has some quality attractions and restaurants. For those interested in history, or the Mississippi River, there is a large Mississippi River Aquarium and Museum located right on the river. The museum is very informative, clean and nice, and is not a bad way to spend a few hours.
The shops of Dubuque are actually quite impressive with many antique and gift shops located in the 'downtown' area of the city. There are even a few local breweries that offer good drink specials. If you like beer you need to visit the busted lift, its the most popular bar in Dubuque and is a great hole-in-the-wall type place to get together with family and friends, and the food is good.
If you have kids there is only one real place to stay, and that is the Grand Harbor Indoor Waterpark and Resort. It is located right on the river and has an impressive indoor waterpark, which is especially nice if you are visiting Iowa in any month besides July or August. The hotel accommodations with the park are a little pricey, but clean and nice.