It can be useful to go onto the Company's website to see if it has pictures of their employees. You can then get a feel of how formal you need to dress.

The individual needs to feel confident in whatever they're wearing.  If they're self conscious about their attire, it's likely to impact of their performance. 

I have previously drafted the following article, containing other tips for candidates:

www.linkedin.com/.../eight-top-tips-candidates-richard-vain

In reply to Sajda:

that's good

In reply to Keith:

Handshakes, one for hiring managers! I often wonder do people want me to shake their hand or do they want me to kiss it, fist pump it, stop holding your hand out like a piece of china or wet fish!

you are better than any qualified person because you cared about the basic need of your child, and the basic and decent dress code for a job interview is Formal suiting and it is easily available on any online store. I hope my suggestion will helpful for you and please feel free to continue asking questions anytime.