I have been to the fancy decoy and call show in St Charles. If you like antique decoys, it is definitely worth attending. The duck call part of the show has really dropped off in recent years. Last year there were only 4-5 call makers with tables. I would not recommend making the trip if you are only interested in calls.
Have you been to the Mississippi Valley Callers Classic in Burlington IA? They hold a sanctioned duck calling contest there every year (Feb?) and there are several tables with calls. I believe there's also one in Peoria, but I have only been to the one in Burlington.