Who will be watching the children while the Mums are watching the thermomix demo? If if were you, I would skip this week. I would hate for them to take advantage assuming you will be watching ALL the kids for them!

And in regards to the original question from your first post, you aren't doing anything wrong. It's them, not you. I would find somewhere else - do you have a local library or recreation centre? They usually offer a weekly activity for the little ones.