Every shower reaches the same deadline: the afternoon you have to tell the caterer how many plates, count the favours, and set the chairs. Reading receipts will not give you that number. People say 'maybe' in a text and forget to follow up. The only honest count comes from answers recorded against names while you still have time to act on them.
That is what the RSVP side of a baby shower page is for. Guests confirm from the invitation, plus-ones are recorded inside the limits you set, and meal or allergy notes attach to the right person. The list shows the shape of the afternoon before it arrives, and you order against a real figure.