The vessels themselves can be available for very little money on Ebay. I think the time and effort spent hunting down a bargain might be badly wasted if you end up with a kayak which drags or is frustrating to manoeuvre. Realistically you’ll only have a few outings a year and you want them to be pleasurable. Buy second-hand only if you have the opportunity to test-paddle – if not tell yourself you’ll recoup the money spent when you sell your vessel.
Canoes are heavier than kayaks and – as far as my 10 and 8 year old are concerned – harder to paddle. That seals it for me. Even kayaks come with rod holders and storage space to allow angling. Many websites recommend tandem kayaks for families. I disagree: we've had great experiences going one adult and one child in two separate boats. You’ll always be on hand but you’d be allowing the child two small victories – firstly the proud fact that they are setting off on their own. Secondly, when things might go awry, they might have a minute or two to reset their course before the adult starts meddling. Purely to build independence I would want children from age 7-8 in their own kayak from the start. Or younger still, on a small lake in fine weather. I’ve read lots of warnings about the difficulties of getting in and out of a kayak and of the dangers of capsizing. It would be a massive shame if this put you off. We’ve had fun for days on end in choppy waters in very steady touring kayaks and my children’s frustrations have related to drifting before steadying their course, not to rolling over.
That’s light touring kayaks we’ve used. You can obviously look into sit on kayaks (wider and stabler than the cockpit ones), children’s kayaks or - if you're raising your game with safety gear and technique - dedicated whitewater kayaks. When it comes to kids’ equipment, customised kit for their height and weight is always recommended by retailers and often the right way forward. But when I’m looking at £500 plus for each kayak, I’m more inclined to let the child grow into the gear I buy. They’ll be teenagers soon enough and in the interim you can adapt your journey length and you can have towing options in place. I really wouldn’t spend days researching this. Be prepared to spend upwards of £1000 all in for two kayaks, paddles and the safety kit and don’t fret about everything being optimal for the age. You’re giving them a taste of a brilliant lifestyle, you’re not setting them up for Olympic success.