Contact a few language mills that offer Chinese for foreigners, preferably in the cities where there are lots of foreigners who will be looking for the best trained instructors (Beijing, Shanghai, and Shenzhen come to mind). Ask them about what sort of certifications their trainers hold, since you want the best possible Chinese lessons.
You can also have your wife contact some and ask what sort of certifications they'd want her to have if she applied for a job with them.
See how many mention this IPA or have even heard of it.
Their US website. ipaus.org
And they seem to have a few more Chinese language websites. ipaceo.com, ipacn.com, ipacnn.com