Yes, some kids have allergies. It's mostly because items will shrink when washed. If you're looking for economical acrylic yarn for charity, Caron One Pound yarn is good. I'm not sure about
Florida with the weather. Here in Wisconsin, hats and mittens are always welcome at the Salvation Army and any elementary school. A school near me says kids come in the office every day looking for something warm to wear at recess. The problem is that swimsuits and summer wear come out in January. You can't buy winter clothing after that but it's still needed. When my son was little, he outgrew his snowsuit in February. I couldn't find one in the stores. Out of desperation, I had to crochet him a hooded jacket. I made it a little big. The bright side was that as he grew, I just crocheted more rows on the ends of the sleeves and bottom of the jacket. He wore it for two or three years. You could probably do this with knitting if a jacket is knit from the top down.