Monthly Mileage Motivation

I am still struggling to find the motivation to get back to healthy habits with some consistency.  I need to rethink goals.  Having a number as a goal (pounds, percent body fat) is not getting the job done.  I know that if I do the right thing consistently, the pounds and the body fat will take care of themselves.  I need a performance goal.  At the beginning of the summer, it was to run a 10K, but that was shelved due to toe and knee issues.  I am planning on riding 50 miles in a bike tour next month, but I already rode 50 miles last month.  With the summer winding down, performance goals have to be more creative.  These goals need to be short term, or they kinda slip away.  

So, I'm thinking about starting a friendly fitness competition for the month of September in my office.  It would be based on total mileage, but since the idea is to encourage cardio activities of all types, every activity would be converted to mileage.  As an example, walking, running, hiking, elliptical, stair master would all be straight mileage.  Bicycle miles would count 4:1, cardio classes would count 4 miles per hour, etc.  I'm sure conversions could be determined for just about anything (strength training does not qualify).  Indoors or outdoors.  Participants keep track of their own mileage, but have to keep some sort of log and provide weekly updates.  Entry fee $10.  Winner takes 50 PERCENT, 30 PERCENT used to bring in a healthy lunch at the end of the month, 20 PERCENT goes to 1 person chosen at random ( cannot be the winner).  Loser has to buy 2nd place a Jamba Juice?

Anybody have any suggestions? Should this be "ladies only?"  Should the number of entries be limited? How can we "level the playing field" so anyone can participate?