I love your blog, too. I might have been a little excited about leaving comments yesterday
Have you checked out kinderbach? They seem to have a lot of theory as well as piano teaching. I finally decided to get them later, because my son is nearly 2 now and I have Piano Wizard for his birthday present to introduce the piano as a game, then use Kinderbach in another year or so when I think he will get the fingering more. I think it could be possible to go through first as a parent with your baby watching, then once he's big enough you can start from the beginning with your son.
There is also tune toddlers for pitch training - I've just ordered them so I can't say how well they work, but lots of people have them. You can get brillkids discouunts, too

I am also impatiently waiting for Little Musician to come out. Unfortunately, I am what you might call 'musically challenged' so am unable to do more at the moment than play music and use a glockenspiel for pitch training.
One thing my son loves more than anything is his xylophone. I didn't bother with the 'baby toy' one and went straight to a designed-for-kids actual 2-octave instrument. Ironically, there is not a huge price difference (I think I paid £15 against £8-12 for a four-note kiddy-toy). It makes quite good quality sound and allows him to 'compose' tunes. He has it in his corner and plays with it often. I also have a larger glockenspiel that we use for our pitch training, which is 'mine' (so he can't acess it whenever he wants and destroy it

) that we take turns playing when doing perfect pitch.