Of course the airplane is a fine choice and your plan is a good one. Most trainers make excellent floaters however I normally suggest not using something with rounded fuselage such as the Nexstar as this makes a good installation more difficult.

The key parameters for success in float installations is pay close attention to the step /CG relationship and the wing /float deck incidence relationship. These two points can make or break a good installation. Float flying does not need oversized engines as some will say but rather good float installations.

Float flying is not at all difficult it is only a little different and normally not a problem at all for someone just off the trainer on wheels and willing to work with a float mentor.

Here are a couple of my ships and the trainer of a young man just off the trainer getting his feet wet for the first time.

John