Thoroughly enjoyed Viking Splash last weekend with my brother and nephew. Great overview of the main tourist spots around the city centre, lots of interesting historical facts (which I've all forgotten already), plenty of roaring at innocent pedestrians, and a quick splash in the Grand Canal basin. It was good fun - and did you know that when you put on your life jacket, you should make sure to unbuckle your seat belt, because there is no point in wearing a flotation aid if you're attached to a 2-ton vehicle!
My nephew is six and doesn't speak English, so I think he was a bit young for it - he enjoyed the roaring and the bit in the water, but I'm not sure he'll remember much of the bits I translated for him (Qu'est-ce qu'il dit, le monsieur?). He'll probably enjoy it more when he is ten.