Keith, sounds like you already got your boat picked out, but if not, you might want to take a look at the Fluid Spice. I got a chance to try it out on the Nile, which is much larger water than you're going to have on the grand, and it handled those rapids like a champ; enough volume and speed to be stable and fast through whatever I could throw at it. It also has a planing hull and slightly slicey ends, so it can do a fair amount of playboating, but it is not a "real" playboat; it has lots of speed for frontsurfing tiny flat waves.
For your purposes, it would be an axiom that would turn faster and stern squirt easier. I think that the Axiom might be faster, though, so you might already be in the right boat.