Are you paddling just yourself or will your son be paddling too? The various strokes aren't that hard to master. I'm sure you can find videos on those. It's knowing when to use them and coordinating with your partner that takes a bit of practice.

You should be fine with the skiing ones as long as they are a true class III (or II but that is bulkier) PFD.

Is this river slow/fast, any rapids at all? You generally want to avoid upstream Vs (obstruction in the water), go in the middle of downstream Vs (water flowing between 2 obstructions) and paddle either slower or faster than the current (ie, not drifting) so you have some control. If there's any significant flow at all, you definitely want to stay away from the really low (or downed) trees. I guess higher ones are called sweepers, the lower ones are called strainers and can kill you. As bluefish said, scan the water well ahead and if you have any reservations at all, head to the shore.