And the "not intended for children's sleepwear" means that the fabric that IS is treated with chemicals to prevent quick burning in case of a fire. I'd rather NOT have the children I know and love and sew for have to snuggle with "chemicalized" fabrics if I can help it!
I'd rather be careful of my surroundings than rely on chemicals for safety, wouldn't you?
Go for the regular cotton fabric with confidence and wash it before gifting.
Jan in VA