I had a similar teaching situation when working for Inlingua in the past.
They had a book for the teacher with the grammar topics to be covered in that unit, and basically you had to make up a lesson from scratch to fit the topic. It was time-consuming, but what was especially difficult was trying to make the lesson more lively than everyone sitting around reading extracts of text and filling in blanks on a worksheet.
Since those early teaching days I have written this book, it would help you.http://www.amazon.com/ESL-Classroom-Activities-Teens-Adults/dp/1478213795
You can try out ideas from the book if you would like to test drive it first. Most ideas in the book may be used with any topic, so that's a big time-saver. There are board game templates with blanks that the class fill in with the required grammar questions or sentences - it's amply explained in the book. There are quiz games, again with blanks so you can adapt them. And discussion type games to adapt to any topic. Also there are language drill type games that may be used to drill anything.
You can get the free samples to try out from this page:http://www.teachingenglishgames.com/esl-for-adults