Ok so maybe I'm biased because I've been here so many times, but this park is a little slice of heaven.  Because the weather on the lake is extremely variable, you never really know what your experience will be like until just before you go.  If it's hot, no problem, you have an ice cold lake a few steps away!  Mosquitoes can be bad, so bring the spray.  

Access to Lake Superior can't be beat - there is plenty of room to spread out and avoid a crowd, if you're so inclined.  

There are cabins to rent, but they typically fill up with reservations pretty quickly.  There are a few campsites that are more private, but in many cases you might have neighbors close by.  There's a fantastic ice cream shop on the far end of the park - you can either hike nicely groomed trails to get to it, or take a car or bike on the paved road.  There's also a good sized playground, large field, picnic shelters, and a horseshoe pit.