Depends on the individual... if you are this easily influenced to worry this and that, that, you will be affected by it in more than one way. It will be endless worries, its about you. If you are not comfortable with it, then choose another date. Simple as that. Don't complicate something this simple.
My MIL and some relatives insists that we cannot say anything good or nice about my baby in his presence, it will bring him bad luck. They also believe I cannot move the bed or do any renovation. I got the bedroom ready for baby, got a new bed and paintwork. My son have not been affected badly by all the good things we say of him.
It affects only the people the believes in them. This is because, we enjoy living our lives, living every moment of it and not sitting and waiting all day to bring relevance to everything to our hearsay beliefs. This is self fulfilling prophesy. When u have a bunch of family waiting for things to happen to pinpoint and blame, they will always find something. It will be very irritating coping with their rants.