I have a Pygmy Osprey, which I have used with my 7 year old son. It is a wonderfully stable boat. I have been able to poke around with it in tight places, and take it on expeditions with rough, confused seas without the slightest fear of capsize. I face one problem: with my small kid, I find myself in an awkward teeter-totter position in which he gets stuck in the air, while I struggled to maneuver. This may be difficult to avoid even in a double. (Okay, I exaggerate a bit, but the effect was noticeable.) I imagine you could load some picnic/camping gear/laborador in the front hatch to minimize this effect. On the other hand, the kid in the middle between two adults works remarkably well.

Good luck.