i (37, bigender/f) have a wife (37mtf). now i guess she has always been my wife. even as a teen, she identified as trans before detransitioning. she wanted to join the girl scouts, too as a kid. i feel like as the wife of a trans woman, she has always been a woman. however, we are so used to her being a guy. i have heard many stories such as “it’s awkward for me because my dad is now my mom” or “i refuse to call my ‘dad’ by ‘his’ correct pronouns and ‘he’ is a trans woman”, stuff like that.
our three kids have always been very supportive of the lgbtq community, though, knowing we are and 2/3 of them being lgbtq themselves.
It doesn’t sound like your kids will have much of a problem, but there’s always an adjustment period with any transition. As long as everything is explained clearly and openly, and they are given some space to adjust, it’ll probably be fine.
EDIT: One thing, you and your wife don’t need to bombard them with details about her transition, unless they explicitly want to know something. In my experience, too much too fast can make the adjustment harder.