Yes, you can opt out of going to Disneyworld.

Not that I'm aware of, I didn't try. They haven't requested my daughter scan her fingerprint at ages 2 or 3, don't know what age that starts at though. During the testing phase the finger print wouldn't always work 100% of the time, they'd get someone over with basically a tablet with an RFID scanner to let you in.

Update for the interested: you can, indeed, opt out of the fingerprinting.

  Are all guests required to use Ticket Tag?

  If you don't want to use Ticket Tag, you can simply carry and show a photo ID that matches the name identified with your ticket.

https://disneyworld.disney.go.com/faq/my-disney-experience/p...