I don't really get the whole debate about canon, to be honest. As far as I'm concerned, be it novel, comic, book, CD or whatever, they're all stories with their own merits. For what it's worth, a sequel with the original actors, produced by Dan Curtis Productions is as about as official as you're likely to get. But, does it really matter if it's "canon"?
All that canon really means is "I like this story less than this story" -- ultimately, it just doesn't matter. If someone likes something enough, they'll make it fit, regardless of how contradictory or illogical it might be. Note how many fans dismiss the Leviathan and Vicki developments off the bat.
I know the original DS episodes from back to front, and much as I enjoy them, there's a finite amount of mileage to be had from them. I'll happily embrace any new stories or ideas, becasue I'd prefer to look forward rather than back. With audios and novels there's a potential for Dark Shadows to feel alive and vibrant, rather than trapped in the past tense. I think it's a great pity if fans really do dismiss new productions out of principle for such a flimsy reason.