Not to sound like a snob but....

I have a sister in law who buys her clothes and shoes only at Goodwill, including her daughter's clothing. She's wanting to get us baby clothing when we find out what we are having. Nothing against Goodwill, but I don't feel comfortable putting an infant--who is susceptible to illnesses--in clothing that has been spit up on, pooped on and used by God knows how many other babies. We've already started buying clothes and my aunt and other family members are wanting to get clothes from reputable places. I don't want to hurt her feelings or come off as a snob..should I just allow her to give us some clothes and put it in storage? Or tell her we already have plenty of clothes, but I appreciate the offer?