Our "Guest Questionnaire" setting can be configured to ask guests questions when they RSVP - note that only the host can see these responses! To turn on the questionnaire feature, go to "Event Settings" and then "Questionnaire." If you add a Questionnaire question after guests have RSVP'd, they'll need to re-RSVP in order to view the updated questions.
Alternatively, you can comment on the activity feed and ask guests to reply or respond with certain emojis to poll responses.