Actually, we have found camping closer to home to be a real benefit. We do take 1 or 2 longer trips each year, but with DS#1 having more health issues, we feel like this trip coming up is our last more than 100 miles. In a way hate to think about that, but certainly won't mind driving past numerous gas stations. Our 2 very fav CGs are both TN SP, one about 35 miles and the other about 45. The rangers are almost like family. It's like being a million miles from home and somewhere along the way, the stress levels of everyday life melt away. We also have a choice of 3 or 4 MS SP or even 1 that's close in AR. These get us home within a couple of hours if need be. We generally pay around $25 per night, sometimes a bit more if FHU, but certainly not excessive rates.
You're in NW IN. What about something around Lake Freeman or Lake _____, that I can't remember. Have you checked into anything in IL? Is it too far to swing around to the MI campgrounds near or on the lake? Brown County is gorgeous, but certainly a couple of tanks of gas - or more. If that appeals to you, make reservations now for fall. We rather like the idea of 1 tank of gas getting us there and back, not spending forever driving, being set up and enjoying the outdoors rather than sitting in the car for miles and miles. There really is something to be said for close to home.
You might also look into some city or county parks. Some are very nice, others not so much.
Good luck and happy camping!