Probably cost prohibitive. Most of the water ways you discuss are surrounded by lots of land - and roads!
Also, they currently charge $210-$375 per hour for their current cruises, with very limited snacks/drinks on board. A dinner cruise of your scope would easily be in the $500-$750+++ range...
If you read the history of the construction of WDW here on wdwmagic, you'll see that one of the first things that they needed to do was engineer a way to maintain water levels across property, by creating a series of canals, levels and other mechanisms. This delicate balance and engineering would need to be taken into consideration to even attempt what you are proposing.
If you look at Google Maps, you will see how each park is almost self-contained as far as water features go.