To customize your response card to allow your guests to let you know their meal preferences, how many children are attending, or which events during a weekend-long event they're attending, you can add an additional RSVP question.
To add an additional RSVP question:
On the Enter Details page, in the "Event Page Settings" section, click on "see additional options"
Click “Add additional RSVP question for guests to answer"
Enter your question, and then save your changes.
When your guests reply “Will Attend,” this question will be shown automatically. If your guest skips answering the question, they can return to the card and the question will be displayed for them again. When you preview your card, you can submit an RSVP in order to see how the question will appear for your guests.
Here is an example: