The success/finish you might get can depend on the particular species (unfortunately I don't know which is the best/preferred!).
I can confirm that it air-dries quite easily, and quickly, and is indeed generally rather featureless.
Depends on your logged size, but 18 months or so seems to be all it needs for even some quite big pieces (big? I mean up 10/12 inches diameter and anything up to the same in depth) to dry out.
However, since you've got 3 trees to play with I would definitely recommend some home-grown spalting. Put some lumps in a plastic bag (something like an old peat bag is good, you need an opaque bag for best results I reckon), add a bit of peat or vegetable material (a handful of old dead soggy leaves'll do nicely), and fold over the top. You're only trying to keep hedgehogs and small children out, no need to seal it up tight. Sling it in a corner round the back of the shed for about 3 months. And then, with a smidgin of luck, voila!, aspen with a bit of character!
It's an easy wood to turn, although not terribly dense - you'll probably be surprised at just how light it becomes when dry - which means sharp edges are required otherwise it's easy to 'tear'.
