I don't think it's tacky at all, possibly a scam, but not tacky if legit. Craig's list also has boards for free items and give a ways.
It sounds like this mom is in a tough position and is doing what she can to get ready for her baby. A lot of items on there are so cheap, it's reasonable to think someone would give them away to a good home for free. I would.
If she were emailing friends or posting on Facebook asking people to buy stuff for her kid, that's another story. This sounds like she's just reaching out for help.