H and I divorced 5 years ago, amicable split and he had our DS 50:50 split with me.
He works full time and his mum will collect DS on a Monday from school however he has now informed me that his new gf will be collecting DS. He has met her online and she's been staying with them for about 2 week now but has pretty much moved in full time. My DS has come back twice this week now saying "He'll cast a spell on people he doesn't like" 
I thought nothing more off it until he asked me this afternoon for a set of robes. I asked a few more questions about why he wants this and was told XW has said I need some if I am join in with her ceremonies.
I'm a active member of the Methodist church and DS is christened, we attend each week. H used to attend but his faith is his business.
I've spoken to him this afternoon to find out what's been going on, he's told me his New gf is a witch, is an active member and he's interested in it a bit now as well. When I asked what DS has been involved in he said he thinks his gf ha probably done a few ceremonies and spells with him and what's the harm ?
Am I being unreasonable to ask that DS is NOT to be involved in this ? It makes me really uncomfortable. DS is 8 and very impressionable.