If you can't or don't know how to paddle a canoe (not that hard really, but some people just don't like the open deck) I'd suggest looking into two additional small craft. A dorry, although an open deck, gives you ALL the control in the boat. Send up a small sail and a lee-board and the kids can turn the tiller.

There are kayak designs out there that are similar to Folbot boats in design. These decks are partially enclosed and allow your child to move around. What's more you can center yourself in the cockpit to maintain the most control of the boat in bad condditions. My son (3 years) were once caught in a bit of weather in the south Puget sound. I tucked him up under the forward deck with some matchbox cars, out of the weather and out of my way, while I batteled the contrary wind and strong current to the shore. He was happy and safe, I was happy and wet!

Speeking of safety, that is always on my mind when I take Justin out, much more so than when I go by myself. Anyway you look at it you'll always be think about that moment that the boat gets tipped. Justin did this to us in my canoe by climbing to the bow of it then leaning over the gunnel. It was cold, we were wet, but as soon as I righted the boat and hauled him up into it the crying stopped and we still laugh at the story when we go out now.