I always wondered about that. My friend is Jewish and he married a Christian woman who converted. I know they celebrate both now, although growing up, he always said that doesn't fly with him. I don't understand how you really do both with any real sincerity.
I'm with you. I have friends he's Jewish she's Christian and they decided to raise them Jewish till 10 then introduce Christianity. But when visiting our house one day their 7 year old daughter ran terrified and screaming when she saw a crucifix over my kids doors and they innocently told her what it was. They had to quickly reconsider their plans.