A line is only half the reply
The wording does the warm part of the job, asking people to answer and telling them the date in a voice that fits your occasion. But a line sits on an invitation, and an invitation needs somewhere for the answer to land. If the ask reads "please reply by the twelfth" while the reply itself is a number someone texts at midnight, the two halves drift apart and the count you wanted never quite arrives.
Put the wording beside a page where guests tap yes or no and the answer attaches to their name, and the friendly sentence does exactly what it promises. Draft the line, set the date, share the link, and let the replies gather themselves rather than reading a pile of messages. You can start free and add a reply line to your event page in a few minutes.