To rsvp or not? That is the question

So, my wedding is this coming Halloween and we've sent out the digital save the dates which includes the RSVP and website.
We have had all of the 'Oh yes, I wouldn't miss it!' but, only a few actual RSVPs. How do you or did you deal with this? Do you just mark their RSVP manually or leave it be and hope for the best?
My concern is, this isn't exactly just a dinner party, it costs a lot per person so I really do need solid numbers in the end.Yes I know it's still soon and I'll be sending out the actual invites shortly, I just wanted some insight.Thanks in advance