On my September sweetpeas 2013 page, anyone who had an original due date in September stayed and would have their due date changed to the end of August or beginning of October. I don't see the difference in changing a due date from May 7 to may 2 vs may 2 to April 30. And if it's too confusing, just leave old due dates. Better to be listed incorrectly than not listed overall, in my opinion. Since no one can edit the first post other than the OP, I get that that's a lot of responsibility. For my Sweetpeas page, the OP would keep up with updates when she noticed them and asked people to PM her if it were important to them for something to be changed. Generally though she just didn't update except I'm batches when a bunch of people PM'd her.
Given how due dates work, a good chunk of our babies will be born in April and June so I vote everyone in included. By removing people, you aren't FORCING anyone out but it is making them less welcome. Just my two cents!
AFM, this pregnancy is so different than my first! I didn't have any symptoms first time but this one is relentless. I am nauseous basically all day every day. It's rough!!