There are many App Scripts available that can add features and tools to Google Docs. Autocrat allows you to merge data in a spreadsheet with a Google Doc and save the merged files as a Google Document or a PDF. It will even email a copy of the document to individuals.
Now let's take the concept of the newsletter and expand it. In addition to adding the person's name at the top, let's customize the first and last paragraph (the middle will be the generic newsletter content). If I'm writing to my brother Bob, my first paragraph will be a personal message to him (eg: Great seeing you this summer - thanks for inviting us to your cabin). The last paragraph is also customized for him (eg: Looking forward to seeing you at Christmas - your room is ready for you!).
After you've gone through and created all this content in your spreadsheet (or if it's easier for you, use a form to enter your info), you can use Autocrat to create the merged newsletters. You can print them off or you can let Autocrat email them out.