Michael, we have run a regular 5-week beginners course (one every 6 weeks) for the past two or three years and they've proved invaluable in helping the dojo grow. The things we've found work best are:
1. assign a high grade (preferably dan) to the beginners for the entire run of the course. This helps the beginners feel they have a high ranking ally in the dojo and helps add a more personal touch to the course.
2. rotate the teacher assigned for each course to prevent them getting stale
3. Keep the beginners practicing separately from the rest of the class for the first two lessons, then gradually introduce them to the rest of the dojo.
4. Have a goal in mind for what you're going to teach them so that, at the end, you can review what you've been through and show them how they've improved and what they've learned.
5. Make the cost of the course cover the full five weeks and charge up-front, but enable people to carry over missed lessons so they get their money's worth.
6. Don't get too dicouraged if you get a 100% drop-out rate at any time, it happens, but the next one all might stay.
Jeanne has a good point re frequency, we can only offer this once a week, but twice a week course would be much better.