I’d always put the money in an envelope with my kids names written to be all magical and fancy looking but didn’t try especially hard to disguise my handwriting. When my daughter was probably eight she just casually informed me how much she had noticed the tooth fairy’s handwriting looked just like mine 🤔 she’s smart, it both let me know she knew what was up but was still low key enough the gravy train kept coming for the rest of her teeth lol