[Angelynn]

I know it is very challenging! I agree with the previous reply about splitting up the group into 2. I would suggest having a theme for the entire class. For example: Grocery Shopping
Give the Intermediate to Advanced a worksheet to introduce the topic, and that is suited to their level. Meanwhile, you can introduce basic vocabulary to the beginners. Once you have introduced the vocabulary you will give the beginners an activity to do. Get them started, and then go over the worksheet with the advanced group. Your 3 hours will be split, going back and forth. You will need 2 lesson plans for each class. I know this seems time consuming (it is), but it will totally pay off in the end. There might even be an activity in the middle of the class that involves both groups. Something more for fun, than actual hard work. You could do charades with the basic vocab words, or pictionary. Regardless of level, it will be fun to get both groups participating.
Good luck! Let me know how it pans out.