My original thought was that the first 3 were bad and, since they are so young they'll appreciate them anyway but... I do not want to blow the father reveal. I'll Probably go with the Erst order.
I'll also wait until next year. My 4 year old isn't ready. I was fine with the first episode being glossed over but not IV and I can't just show it to my 5 year old.
Thanks again!