Hi Ruth Ann,
As you mentioned retention is the key to not only student success but college success as well. These students need to remain enrolled and the college and instructors need to do whatever they can do keep them enrolled. The above statements are essential we know, the challenge is how to make them work.
I do have one suggestion that goes beyond what you are already doing. Depending on your class and the policy of your college you might be able to break out portions of the course in such a way that the students can see how they can learn that part of the content and then move on. With the short time span and the concentration this may be hard to do. We schedule support sessions and tutorials to help while students are working on activities within the class. Also, we use one on one supports with peer tutors or mentors. The key is to find something that will give students support and will work within the confines of your college/course setting. It is hard for me to give a specific answer without having the complete picture of your setting. Hopefully these ideas will get you to thinking about ways you can keep the students enrolled and engaged in the learning process.
Gary