Oshkosh. USA. 2017/18

Has anyone had recent experience of visiting Oshkosh and staying there for the week?
I’ve always wanted to do it but getting practical advice is proving difficult. My plan would be to fly in to Chicago with my wife and another couple, rent two motorhomes and camp at the venue. I’ve sent a few emails to the EAA website but only got one reply and then it didn’t answer all my questions. Apparently the reservations for camping sites don’t open until 30th June! which isn’t much use if I’ve spent a few thousand on pre booking air fares & motorhomes only to find three weeks before the event that there isn’t anywhere to stay.
Are there any other websites where I can get information and can anyone recommend alternative camping sites in the area?
Any practical advice would be most welcome.