For family canoeing an open canoe would be best so you've already decided that. :mrgreen:
Almost all of my experience comes from slalom and white-water both racing and running big water, in a K1 kayak.
Have a look here,
http://www.songofthepaddle.co.uk/forum/forum.php? loads of info and friendly advice. There seems to be more than a fair number of us Scots on there too so you might know a couple of them, me and The Ken.
We bought an open canoe a few years ago to paddle on Loch Leven and elsewhere but the elsewhere hasn't happened much.
Ours was an eBay auction 2nd hand but guy was up north on edge of Cairngorms somewhere. Collected it on the roof of my wife's Panda, a 17'6" canoe on a Panda. :shock: