We spent a summer in Grand Haven and have been back a few times.   The municipal marina should be fine. Where you can have issues is on the wall closer down towards the lake. That can get bumpy in the right conditions. We haven't seen an issue with the actual slips. For a short stay, it's the best option in our opinon.   North Shore across the river is fine as far as facilities but it's not convienent to town.   Grand Isle is a nice marina just past the US-131 bridge. It is walking distance via a nice path to downtown.   There are a couple other marinas over on Spring Lake but access to town becomes less convienent.