From their website, it looks like there are three ride options, a full century, a 50k, and 75k. If you don't feel up to the century, the 50 and 75k are very doable goals. You have more than enough time to build up to those mileages. As you know, most of central Indiana is flat, so while I suppose they could route you over the fews hills that do exist over by Eagle Creek, but they're not bad at all.

You might do a search for Tour de Cure on TE. I vaguely remember another member doing the ride last year, but I can't remember her name. I bet if you PMed her, she could give you some information as to well organized it is.

I'll be honest that while I think it's a great cause, I've never had any desire to do the ride because the century option around the track is SO unappealing to me. I wish they'd offer something else. If you do decide to do the ride, please PM me; I'd be happy to make a pledge.