It IS necessary, that's how you get your room ready text, etc.
If you go on to My Disney Experience,
Log in
Then in the upper left hand corner are 3 bars.
Touch the 3 bars, it will bring you to a list. On the list is
"My Disney Experience"
Touch that icon,
You will come to a page that offers multiple choices, near the bottom is:
"Contact Information"
Touch that icon and it will bring you to the page to update.