So, you want things like assertiveness training? I'd suggest at that age maybe approaching a drama coach? Doing role play type scenarios of equality issues. Racial/bullying/sexual etc and how to handle. Here in the uk there are actor groups that do this kind of training when not acting. Seeing it live and getting the students to correct and advise the adults in the scene can be very empowering.
A media course obvs. Using fb/twitter to their advantage. CV writing. Creative writing maybe. Dressing for success maybe?
I think framing it round leadership/confidence building might help - I'm taking from your OP you think a few parents might not be that in to their DDs attending something branded 'feminist'?
Something which would attract me as a parent might be around staying safe online, building confidence round peer pressure, effective strategies for looking after each other. But then as Minnie said these are serious topics so some role play/drama type way of delivering it to make it feel like a fun day would also be good.
I saw a similar thing run by clinical psychologist once called 'find your inner awesome'.
Covered bullying, peer pressure, body confidence and safety online and offline (covered FB, cyber bullying, being uncomfortable on dates/around sexual pressure: saying no), setting goals, and group problem solving. They did a session of being agony aunts for a girls magazine, brainstormed what beauty/body advice and images they'd like to see in the media and finished up by prepping food to take for a heathy lunch, going on a hike finding clues to a treasure box which contained a key ring with their group photo on.
Mum I know sent her 12 year old and was v enthusiastic.
If teens, which plainly I assumed above, could you do something 'apprentice' like? I ran some things for grads doing banking training where a charity for homeless (for eg) asked for a shopping list of stuff and the participants went off asking for local business support to donate. All the items went to the charity and the kids had run a project. It was really good fun - and empowering as it mattered. You fail the charity lost out.
Equally they could raise money for a charity, cakes/biscuits/soap making /yard sale whatever but put two teams and complete set tasks.