Hi, I try to dress our 7 month old baby in 100% cotton outfits or sleep bags. However, coming into winter, I've noticed some warmer feeling fabrics have polyester mixed in. For example, a onsie with 75% cotton and 25% polyester or a sleep bag with 100% cotton fill but 95% cotton and 5% elastane arms and sides. Are there any guidelines on whether polyester fabrics are safe for sleeping? Are small amounts like 5% or 25% ok? Thank you very much.