Your Say I do wedding website will ask guests to enter any dietary requirements automatically when they RSVP. This information will be saved alongside their RSVP information so you can hand it off to caterers when the time comes by simply exporting your attendee list.
Can I turn this question off?
Yes. Just go to your RSVPs, then click RSVP questions and toggle Dietary Requirements to Off.
What about adding other questions?
You can add as many custom questions as you'd like. See the instructions here.