For the big kick-off, educate your staff about specific elements of the program and make sure you have relevant items to gear everyone up to invest more in their health.
A high-quality rolling duffel bag would be great to take to the gym and would be a welcome gift for people who hit their fitness goals.
While diet and exercise are important for healthy living, don't limit yourself to only those components. Gift employees with journals to write their way to better mental health, or stress relievers for coping with daily tensions - even for help with smoking cessation.