Disclosure: I am a "legal" ALIEN.

I think the OP's question is valid, although uneducated. Please take no offense, but I have to suggest that most average Americans are sadly uneducated on the immigration/work permit/visitor Visa process.

I have been irked to-no-end lately, seeing the use of the term "immigrant" used in the mass media to describe any non-citzen in the USA - regardless of their status within the petition process.

I have 7 years in the US on a series of TN and H1B Visa's - costing my employer and I over $10,000 in legal and ICE fees. I proudly proclaim myself to be a LEGAL NON RESIDENT ALIEN. If the Immigration gods smile on me, Mr. and Mrs. sqwert will soon hold Green Cards, and therefore be known as "petitioning for immigrant status".

Would I counsel the OP to take the nanny on a flight ? Hell no ! Mrs. swert has been pulled into secondary immigration screening on several occasions merely because she is holding a H4 Visa. I cannot imagine the nightmare that the nanny (and children under her care) would suffer with no documentation to support her residency.

To the many and various comments about the difficulty of entering the US legally, I say: I can understand why. Until 2006 Mrs. sqwert was not legally allowed to hold a Illinois drivers licence - because she does not have a SSN - even though she is legally a "non-resident alien". Being legal is painful and expensive.

End of Grr.

I hope all goes well for the OP and Nanny !