There is a paved bike path that goes from Grand Haven south to Holland (about 20 miles one way). It's a nice ride and follows a road called Lakeshore Drive.

As far as bike rentals go, you can contact Rock N Road--they do a lot of rentals of bikes and trailers. They also have maps for popular bike routes available.

I'm a Grand Haven native so if you have more questions, feel free to PM me.