I grew up in SE Michigan and spent my childhood camping at the Pinery. I haven't been back in three or four years, but it has always been an amazing place.
There are some great (relatively short and easy) hikes, a massive beach with perfect sand, and a very friendly staff. It gets really busy during May 24 holiday, and american Memorial Day weekends, but the part is really big and can handle it.
The Roo is perfect for this campground. Lots of back-in sites, but there is plenty of room. Most of the sites are fairly private, and the bathrooms are clean.
If you are in interested in other camping in southern Ontario, there are a number of excellent campgrounds - we like MacGregor Point (https://www.ontarioparks.com/park/macgregorpoint
) better than the Pinery for example. Even a little further north are couple more great options like Cape Croker (https://www.capecrokerpark.com/
) or Bruce Peninsula NP (Camping - Bruce Peninsula National Park
Have a great time!