Best Way to Have a Back-and-Forth with Non-Users?

I have a sheet with info for a few hundred people. For privacy reasons I cannot share it with them, because they cannot view other people's rows (a selectively hidden feature I've put in a vote for). 

So I send everyone their information in an update request and ask them to fill it out. I then see their answer, respond, and it sends an update back to them on their data again plus my response.

But sometimes there is a need for more correspondence and we have a whole back and forth. Is there a clean way to do this? The only way I can think of is to have several Q&A columns, for me and for them, where when I ask a question that automatically sends them an update request, and then they answer by filling out the form, and I see it and respond again while at the same time sending them my last answer, etc...

I would even resort to email because that would be much cleaner.



Thanks for any help