If you go to the 'insurance' tab above you can see the various categories. There should be one for 'group fitness'. You probably want to talk to the insurance agent directly, or send them an email to give them your specifics, so they can give you a quote. The agency providing the insurance is not IDEA itself, though IDEA members get a good rate buying it in this way. It seems likely you would buy one policy though. I have one policy written to cover me both for group fit and for yoga.
I also agree with Ariadne: