Have a part of your time to learn the latest slang. Get the adults to do the motions, too. Let them know it is slang.

I take it you are teaching SVO structure. That's good.

Short oral presentations (initially a minute is good, but allow prep time of a half hour) work. When they are comfortable speaking in front of their peers, have them reach in a bag, remove an object and give an extemoporaneous talk on it in which they have to describe it, speak to its utility, etc.

Take simple songs and rewrite the lyrics.

I neglected to ask, how long are the classes?