How about the Missouri River?  It is a slow moving lake and very nice.  Great views and you have it to yourself.  You can spend hours and see only a couple of john boats.  Unlike the Mississippi, the Missouri has very little barge traffic, but if you happen to encounter one, give it a wide birth and make sure you paddle straight into the wake.  Don't let it hit you broadside.  There are wing dikes and bridge supports, but it's  a big, wide river unlike the Ozark streams.  It's very much like a lake.  You can camp on the islands that have sand bars.  There is more than enough driftwood for a fire.  Check river forecasts to see if it's going up and place tent/kayak/canoe accordingly.