Frederik Meijer Gardens & Sculpture Park is a 158-acre botanical garden, art museum, and outdoor sculpture park located in Grand Rapids Township. (Kid friendly!)
140 acre zoo located on the west side of Grand Rapids. Another great option for those visiting with kids!
If you've never visited Lake Michigan before (or have only seen it from Chicago) we highly recommend stopping at one of the state parks while you are in town. Holland State Park is one of the closest options to downtown Grand Rapids.
Another great area on Lake Michigan, just a little further north.