I would suggest not getting any of those, instead get a newer age playboat.
Especially if you guys are going to paddle class III, playboats will be a bigger aide to becoming better all around boaters. If your son is young and into it he will benefit being able to learn cartwheels, hole/wave surfing, back deck rolls. Not to mention park&play is great for anyone that needs work on their roll and eddy practice.
My suggestions- Project 52, pyranha 420, Jackson star/fun series. These boats are fun down river playboats and great boats to learn the basics of boating in.