Privately my kids call me dad, because after all, I will always be their father. In public it would be a little weird for them to call me dad so we have settled on Dee or "D" which is short for dad. My kids are 29, 23, 21, 20 and 17. The one rule I've always had is that they don't get to call me by my first name. That was the rule before transition and it is still the rule.