Children and toddlers mistreating 3 month old baby?

Wow. You definitely have a problem here, and your sister is a good part of it. I will guess that those kids don't get much attention from her - the fact that they do stuff and then look to see if she's looking says it all. They are seeking attention - even if it's negative - and they're getting it from you by mistreating the baby. Your sister needs to be made aware of this, and NEEDS to start spending time with her children in a more positive way. I wouldn't hesitate to give those kids a what-for myself if that were my baby - no way would I remain quiet about it! I understand you are relying on your sister right now, but you don't have to tolerate that treatment - the sooner you talk to her about it, the better. This is NOT a "kids will be kids" subject AT ALL. BTW - not all daycares are slimy - there are some very good ones...where spitting on and smothering children won't be tolerated. Do your research on them by asking other parents, etc. It might cost more $$ that way, but the safety of your baby is worth it.