Welcome to the forums Jared,
The general rule to go by is that campgrounds with shelters have picnic tables,
even at the group sites. Only campgrounds on Lake Superior have shelters but not every Lake Superior campground has a shelter. A slightly better indicator of which Lake Superior campgrounds have shelters is which ones have docks as they also almost always have shelters with at least one exception, Hay Bay, but you won't be hiking there as Hay Bay is not on any trail. Makes me wonder if Hay Bay has a picnic table?
Your best source of information regarding docks and shelters is the chart on page 6 of the
2016 Greenstone, the park newsletter. At the shelterless, dockless campgrounds, you will occasionally find resting spots improvised by previous inhabitants (rocks or logs), left in place for your enjoyment and comfort, but don't count on it. Another campground creature comfort to bring is a pair of lightweight "lounging" shoes, like Crocs, moccasins or even slippers.
If you are disappointed, finding your group site without its picnic table you hoped for, try looking around as they can sometimes "walk off" and end up at a different camp site or even on the dock. I always planned my itinerary to highly favor Lake Superior campgrounds but not for sitting amenities but because I simply love being by the Big Lake for a whole variety of reasons including the breeze (less bugs and cooler temperatures, although that can be a negative sometimes), the sunsets, the sounds (for sleeping) and better tasting water. But don't be too concerned, spending any evening or morning at any of the inland Isle Royale campsites, with or without a nice place to sit, will a fantastic place to be. You will have a great time regardless your itinerary or posterior appointments.