Translation:When the baby sleeps it is a good baby.
I think you mean, "dann", because "als" doesn't mean "then", but "than" instead. I think you're right, I just thought this form with "then" sounded more... english :)
Why is it 'ist es' and not 'es ist'? Is it some kind of word order rule that I'm unfamiliar with?
It is "ist es" because the verb is always in second position in a German sentence. The "wenn" clause occupies the first position, so "ist" must come next.
Looks like every time the subordinate sentence comes first (Wenn das Baby schläft), it brings the main sentece verb near it.
Why "... it is a good ..."? Shouldn't be " ... he/she is a good ..."? Is this a kind of politically correct expression? In this case it should be "she" ... I think.
in german, "baby" is neuter, so they refer to a baby as "es." even though we don't use "it" to refer to babies in english, the baby's gender is not specified here, so that's the best we can do.
Tried "as long as the baby sleeps", I believe it's better than "when", since Wenn has a "only if" meaning.
Wrong =....but I'm not sure enough to make a report.