I second getting a crossover boat- something like a Jackson Traverse or Karma RG. The crossover boats can still paddle whitewater, have plenty of room for multidays, and many have a retractable skeg. The skeg is AWESOME for helping the boat go straight. When I'm paddling around on a lake, I find that the super turny whitewater boats use a lot more energy just to keep them straight.
I own a Karma RG for luxurious multidays (so bringing a break down fire pan, folding chair, full tent, maybe a soft cooler with ice, groover tube if required, etc) when not going ultralight (sleeping under a tarp) or running rapids I find challenging. It's a blast, and makes camping w/ the gf much more civilized. Fast on whitewater. Goes straight on flatwater.