There is nothing you can do to quilts to make them fireproof. I wouldn't add anything due to potential for allergies.
Soapbox ahead: The concerns for having fire retardant for children's sleepwear was based on iffy sampling (can I say junk science?) back in the 70s. Most fire injuries occur to children when they have regular clothes on, not nightwear. While required to prove that children's sleepwear retains the retardant properties for 50 washing, in actual tests at some universities, additives such as softener sheets and various whiteners can eliminate the retardant in as little as 5 washings. The part of the law requiring CLOSE FITTING garments makes sense, given that a large increase in fire injuries resulted from the popularity of wearing oversized T-shirts, but then parents should know about this for clothing for any time of the day, not just nightware.
Some other info.
http://green.yourway.net/3-ways-to-g...fuzzy-pajamas/