/Deunhouwer - Charlemagne on Ton Deunhouwer's file of 100,000 descendants - "Allowed copying data and persons (under construction) for own risk!!!!!!!." - Descendants listed are stated to be as follows (our generation number followed by number): 2/11, 3/14, 4/23, 5/35, 6/57, 7/83, 8/98, 9/105, 10/119, 11/128, 12/155, 13/139, and so on up to 43/10 (totalling 20,605); Familypedia has more for the first half dozen generations and is likely to have many more for the rest as time goes on. See Project Charlemagne/count.
/FFish - FFish - "Johnson & Wallace Family History with the Fish & Kirk Family & Others" - Massive family tree table "Created by Legacy 6.0, http://www.LegacyFamilyTree.com", arranged by generation, noting duplicate lines, extending to over 40 generations with easy links and extensive references. Apparently at least 1119 people, spread fairly evenly over the centuries. Says "Charlemagne had seventeen children". Well worth checking even if not complete for any generation?
FJaunais not the best source, but sometimes the only one for France
e-familytree.net, a compilation, by Rob Salzman of Oregon, of over 750,000 people linked somehow to Charlemagne; clearly far from comprehensive (though it may contain more descendants), because it gives him only one child.