have you considered an inflatable 2-person pack raft or kayak?

For Camas Moon, I opted for a 1-person packraft as I wasn't willing to tow anything. It weighs only about 5-6 pounds. When deflated it takes very little space and can be stowed almost anywhere. I think the 2-person versions are about double that weight, but that is still very light compared to any hard boats. It takes about 10 minutes to inflate it and get it ready.

CLC's observation about low-inertia boats is spot-on for a packraft, with the additional downside of them having the directional stability of a beach ball. However, as I primarily use to get from the boat to shore in calm-ish conditions, I don't see it as much of a drawback.