Critical Thinking is a bit difficult not only to define but to come up with activities to develop that skills and to motivate them to do so cause we know most of our students don't like to think outside the box or think at all.

Using videos and stop in between and spark up a conversation then continue to see if what they would predict would happen would motivate them.

Scenarios/role play/ what if they would enjoy that instead of answering open ended questions. make the questions or problem real life. 

Allow them to test and evaluate their findings/ responses.