Audubon Wildlife Sanctuaries Michigan Audubon’s phone number is 517-641-4277. You might want to inquire first before going out to these trails as I am not sure just how easy they are.
Bernard W. Baker Wildlife Sanctuary has the Iva E. Doty Native Wildflower Trail, a one mile self-guided trail. The trail, “with an extensive boardwalk, winds through a wet meadow, past a quiet pond and woodland creek and along the edge of a flood plain forest.” A self-guiding brochure is available at the Doty Shelter.
Phyllis Haehnle Memorial Sanctuary has a loop nature trail and an observation site. The observation site is wheelchair accessible and I think the trail would be easy. This is a great place to see cranes in the fall. Map
Otis Farm Bird Sanctuary According to the book “Best Easy Day Hikes Grand Rapids, Michigan” by Kevin Revolinski, there is an easy grass and packed dirt 1.9 lollypop trail here going through wetlands, hardwood forest and prairie.