Yet Another Mail Merge (Tutorial Video)
To save time, Yet Another Mail Merge lets you personalize the message to each individual parent. All you need is each parent's e-mail address. Comments or messages are typed into the fields of the spreadsheet and then merged into your Gmail. The add-on pulls each field you want from the spreadsheet. It then creates an additional column letting you know exactly when the email message was delivered. Very slick!
Below is a very helpful video tutorial from Michelle Armstrong showing how it works.