While the 5yo have some understanding of the differences between boys and girls, I really don't think that the 1yo has a clue. And any attempt to explain it will be lost. If you transition while that one is still quite young, she/he may never have any memory of you as anything but male.
The 5yo may be approachable and actually have an idea of what you are trying to say. So just be yourself and speak honestly. But remember that they have very short attention spans, so if you are expecting a real heart to heart, then you may be disappointed.
Keeping it practical and to the point is probably best. For example:
"You know my name used to be (insert female name)"
"yes"
"Well from now on, I'd like you to call me (insert male name)"
"ok"
If they have a question, they'll ask you, children can be embarrassingly direct. And if they want to know why, just tell them the truth. For example:
"why?"
"I'm going to become a boy and I won't be a girl anymore"
"will i ever change into a boy (or girl)"
"No, it isn't something that happens to everyone, you don't have to worry about that."
"ok"
"I may grow hair on my face, but it will be alright"
"will it be scratchy?"
"I hope not."
Children are direct and usually frame changes in their life in the context of how it will affect them. And when a question pops into their mind they will probably ask it as soon as it occurs to them. Usually in a public place like a restaurant. At the top of their voice.
As they get older they may have more questions or want to discuss it more, just handle it at their pace.
-Sandy
