Well, if it were me, I'd focus on where people likely congregated to spend money. Likely not on the immediate river bank, but somewhere nearby where they undoubtedly had food/drink sales or just up from the bank where they may have had picnics. Look for any flat-ish spots where you could locate something like this. The rivers change so much over time and move material around, its hard to say if it looks the same. If i were hunting the creek area, i'd wait til mid summer low water and look for bedrock, and then detect in areas where the water action has moved the rock around and allowed coins to settle to the bottom. No doubt they went swimming and lost a few items. Move the rock until you find the bottom, and that is where the goods are in my experience - always right on the bottom mixed in w/ iron and often stuck in cracks.. Finally, they likely had changing rooms near the river, and that is more likely to be where dropped good are than on the river bank.

Good luck. Sounds like fun!

ZIncoln