First off, a big thank you for the comments. It's nice to know that someone is actually reading this, and might even be moved to say something about it - even if I have no idea what Neil is talking about most of the time!
NickF however raises an interesting point, with which I would agree wholeheartedly. The question of Decide Your Destiny books came up recently during one of the interminable debates on Outpost Gallifrey over what does or does not constitute "canon" - (the correct answer of course being everything and nothing - but I will write here about the futility of canon debates some other time...) One of my correspondents had decided that only broadcast Doctor Who performed with live actors could be considered canon - but later decided to add an exclusion clause for Attack of the Graske, because it was "only a game", even though it fit all his other previously-stated criteria. But that's canon debates all over - arguments are continually fudged to fit an individual's preferences.
For the purposes of The Complete Adventures, I had no problem at all accepting Graske, the Decide Your Destiny books, nor any of the earlier Find Your Fate volumes as bona fide Doctor Who stories. The major argument against their inclusion (the "only a game" gambit) is that they depend on the input of the viewer/reader to decide their outcome. My answer is that the game aspect is something of an illusion. The outcome (or outcomes) is a given, provided in the text of the book, and the reader is guided through a series of choices to arrive at a pre-determined conclusion. In the case of some of the books (and indeed Attack of the Graske) the choices are very narrow indeed, leading you via a few diversionary paths to a very limited set of outcomes. So, the complete adventure is there - it just has a few variations. As NickF says, this is the very definition of the quantum universe hypothesis I've proposed.
There's a flipside to this of course, which is that some things really are "only a game". I would place things like Destiny of the Doctors and earlier computer games, role playing game modules, and even those "paper counters and dice" board games that used to appear in Doctor Who Annuals (some of which have quite elaborate backstories) as adventures that might have happened to the Doctor, but which have been inadequately recorded. Their narrative and conclusion, being defined solely by player involvement, makes them a sort of "potential reality", and for that reason they haven't been included in The Complete Adventures.
I was also recently asked about some of the more extreme additions to Doctor Who - educational books like the Doctor Who Discovers series or the Quiz Book of Dinosaurs, and whether they ought to have been included. My main reason for ignoring them is for the sake of my sanity. My get-out is that they're not actually adventures, and so don't fall under the remit of my site. I suppose they too come under the category of "potential reality", things the Doctor might have got up to (setting vaguely educational quizzes for his companions during the time they weren't busy having adventures and saving the universe and so on...) Rather usefully, the Doctor Who Discovers series was ret-conned by the Big Finish play The Kingmaker into a series of educational texts penned by the Doctor himself during his fourth incarnation - so it's quite possible he continued this writing career subsequently, and the Quiz Books are the result.