Here is the research I've done.
First option.
http://www.michigandnr.com/parksandtrails/Details.aspx?id=457&type=SPRK
This is the PJ Hoffmaster state park. It seems to have some cool things that we could do. There are trails and an observation deck. For tent sites I think it said $26 per night.
Option two
http://www.michigandnr.com/parksandtrails/Details.aspx?id=475&type=SPRK
This is the Muskegon State Park. The price is about the same, and also has trails, and such. One benefit, it's close to the channel (north muskegon side)
Now, here is our old standby - Pioneer Park.
http://co.muskegon.mi.us/parks/pioneer.htm
One bad thing about this, is there is no reservations. We'd have to take a chance.
I did check out a few other sites, however, they are a lot more expensive.
I'm sure there are other sites that were not listed on the website. I'm voting for Hoffmaster. We can make reservations, it's close enough to be able for those who may need to work, they have a lot of places the kids could explore, and it's on the beach.
Now accepting feedback.