I really like the idea of a "baby-language".  But I also think, why only babies. For example the conlang Ido is a language made to be spoken world over. It's simple grammar + vocabulary. No exceptions. And a baby would easily learn it. 
And, I think it's kinda weird to teach another baby your conlang..

> Date: Tue, 6 Sep 2011 22:37:18 -0400
> From: [log in to unmask]
> Subject: baby's first conlang
> To: [log in to unmask]
> 
> Hello all,
> 
> Recently I've been wondering: what features should a conlang designed to be
> a child's first language have?
> 
> This question occurred to me while spending some time with my friend's
> niece, who is about 18 months old.  She's picking up language at an
> astonishing rate, although her pronunciation is lagging behind her
> comprehension.  Naturally I thought of teaching her a few words in Angosey,
> my conlang, but the opportunity did not present itself and plus I would hate
> to inflict such a strange language on anyone!
> 
> But this got me to thinking: what if someone created a conlang specifically
> to be learned by a child of about that age?  I know for example that
> toddlers can be taught ASL, and can actually communicate in it better
> because their motor control is more developed than their ability to produce
> sounds.  However, what about a spoken language?
> 
> What kind of phonology would it have?  I think it should have very few
> sounds, and ones relatively easy to pronounce and very distinguishable.  
> 
> I assume that the grammar should be perfectly regular and also simple,
> without a lot of conjugations or inflections.  Does it make sense to have
> invariant word order?  Or is the fact that I think invariant word order is
> simpler than, say, noun cases, a bias of having English as my L1?
> 
> Thoughts?
> 
> Danny