I was just there last Friday, and while the lines were longer than an average weekday, they were probably only about 5-20 minutes (Maybe around 30 for High Roller and the Mouse).
Valleyfair is a smaller park, so you shouldn't have much of a problem with getting on everything if you stay until close.
My recommendation, make Renegade the last ride of the night. It's fantastic at night (And if you have the time, just spend the last ~hour marathoning the thing in the back because it's amazing and way better than anything else at the park).
THX! We'll probably give it a try tomorrow evening