I'm trying to organise a birthday party for my soon-to-be 6yo and her friend. She's quite girly, and the mum I'm splitting the party with would like to have girls-only to keep numbers and cost down. I think this makes sense. My husband and I are both feminists and he's uncomfortable about dividing the class between girls and boys. He thinks the division is arbitrary (it is) and not a model for how he'd like society to be. We don't have all the money in the world, so can't rent a hall, etc. to be able to host 30 kids. The other mum at the moment is offering to host in her house. Beyond the obvious and practical, any arguments I can convince him with? I'm really quite annoyed!