baby name opinion - what should I do??

My SIL (Sister in law) & brother just recently asked me to be the god mother of their baby. They don't know the gender but they have baby names picked out. My SIL asked my true opinion (SIL knows I'm truthful & blunt) because they are on the fence about their girl name. SIL said "please help us, its important"
I don't want  be rude but I don't like it.. But I don't want to tell them that, I want them to like the names they chose & most importantly ITS NOT MY BABY. But they told me they want me to be involved in the name picking. Should I fib & tell them it's a go? I don't want to coheres them into naming the baby a different name just because I'm the godmother.