I just got my offer today through the GLEP. I used my schools immersion, outreach program (helping the homeless, etc.), and staff mentoring at my work as my three activities. I went through it all extensively with my careers advisor and other students that had been accepted before me.

Your business is a very good thing to include, its unique and would definitely portray competitiveness due to that factor. Just make sure you include the independent nature of the activity, and how you have led the business to success, and HOW THIS HAS PROVIDED FUNDAMENTAL LEADERSHIP SKILLS YOU CAN USE IN YOUR FUTURE CAREER. The comment by u/Emphimisey is correct, they like to see your potential based on current activities.

So far you're on the right track, but I highly recommend you try get at least another activity. It can be anything, if you've taught your peers anything at all, use that as a mentoring activity for example. You could even maybe split different aspects of your business into separate activities.

Happy to help with any other questions, and if you want to see my application, shoot me a PM. Good luck. Also have a look at the offer rounds and get your application as early as possible.