FTR Visa gift cards wont work at the post office.
AFAIK there is nothing illegal with depositing MO's at your bank. you can deposit millions and you wont break any laws.
The risk is in your bank not wanting you as a customer because of the elevated risks involved, primarily compliance risks.
Another small risk is reports filed by your bank to the gov't.
Anecdotally WF is from the more lenient banks in this regard, however if it's a new account, I would take is slow with any institution.