I've seen a couple of the Coleman inflatable kayaks in stores. They look like deathtraps for whitewater. From what I've seen, they're far too soft. They won't bounce or slide off rocks, they'll wrap around them - potentially with you still in them! I could see taking one down a class II to III- wavetrain. If the rapid has any rocks in it (as they sometimes do!) I'd feel safer just jumping in to the rapid and swimming.

There are some high-performance IKs out there that can be paddled safely by experienced whitewater boaters in class IV-V rapids. They start at about $1000 new though!