I would just ACH the 100 if you're worried.
I would use my ATM card at a grocery store and get cash back. It's surcharge free.
This also reminds me, I have to get my PenFed ATM card. I never got one when I opened my regualr share account. It soulds like I have to call PenFed to request this. Their ATM request link is broken
check if your atm card has block card feature so you can block and unblock when it's neccessary. I know some of other issuers have that.
the differences between atm card and debit card are the atm card for withdraw ONLY. Your $$ is safe unless your card is lost/stolen