I have a similar dilemma with a twist. I am helping with planning an event for about 100-150 people also, with about 50% being out-of-town, so I also need a room block.
The twist is that the location needs to be near a golf course and the hotel needs to provide transportation from/to the airport for our VIPs. Two places that have popped into our minds are Oak Brook Hills and Seven Bridges Marriott/Hyatt. Does anyone else have any other suggestions?