Well, the only way to be sure is to try. However, I would never encourage anyone to use candy in an incentive system, for children or adults.
For anyone interested in using an incentive system, I would suggest that the first step would be to brainstorm lots and lots of possibilities. Here are a few ideas and considerations to get you started.
In my piano lessons at age five, the teacher would put a sticky star on the page once I had "finished" a piece. There were three colors. Gold was the best, of course.
Sometimes it is helpful to let the student self-evaluate. (As an example, you could offer the three-bin box of stars and ask if she wants to choose one. She could then fish one out herself, or point or tell you a color.)
One of the most effective incentive systems I ever saw for my son, who was 10 at the time, was the following: his art teacher kept the kids motivated to stay on task by reminding them from time to time that the reward for productive work was a popcorn party at the end of the month.
My dentist has a basket of inexpensive toys for the patient to choose from at the end of the visit. I'm thinking, if a large number of your students are mothers, they might enjoy picking something out to take home to their child (not every day of course). You can get some real bargains at thrift stores. Also try the party favor aisle at a big box store. Children may like a strip of animal stickers, a tiny box or a strip of fake tattoos, a fancy pencil, silly putty, Groucho glasses, etc., etc.
That's just to get you started. This list can be expanded.
But I wanted to bring up another aspect of this. You mentioned they "complain about the time commitment or workload" and you mentioned also the challenge to "complete assignments on time and are prompt with meeting deadlines." This makes me wonder what the homework load is. I remember in college the rule of thumb was to expect to put in 2 hours on my own for every 1 hour in class. Of course this is quite variable but that was a general rule of thumb I heard at some point. What is the ratio you are anticipating to be needed by your students, on average?
A homework to classwork ratio that is difficult for your students to carry out might be part of the root of the problem.
If so, it might be helpful to design into your program some required or strongly encouraged "lab" hours. The "lab" could be staffed by a minimum wage person (as opposed to you, who hopefully have a substantially higher pay rate). The "lab" could be the place where the homework assignments are done.