Group Fitness Class Marketing

I run a daily group fitness class for women and moms. We workout at a local park. The kids run around and ply or join in while the moms get in a circuit workout (cardio & strength, followed by stretching). The price is set at a punchcard fee ($6-$9).

I live on a military base overseas and so many people offer their services here for free! There are no less than 8-10 group training offerings, from circuit style to running groups to beach body coaches getting groups together to do the workouts. Not to mention that all the group classes offered at the gym are free (although no children are allowed, nor is childcare provided at the gym). Most are not offered by certified or insured professionals.

I have a loyal following and have offered referral programs, contests, family days, but few new clients are coming. I've run this class for 10 months now and still am working 5-10 sessions for free without turning a profit. How do I compete in a marketplace where people are giving away their services for free and the clientele don't care if you're insured or certified?