To do there - hike the dunes, hang out on the beach, take the commuter train into the city (i.e. Chicago), hang out at your campsite, visit Indiana DUnes National Lakeshore next door - just for starters. The CG at IN Dunes SP is great, and very popular (be sure to have reservations, whether weekend or weekdays - and this advice stands for Turkey Run as well). Nice big sites, lots of space between them, for the most part. We've never spent more than a night or two there, on the way to somewhere else, but several nights there would be fine. Personally, I'd recommend staying there during the week, rather than over the weekend; it's likely to be a bit quieter (especially on the beach).
