For what is worth, from what I'd seen til now and from what I get logically and intuitively, children (of any ages) usually are the ones who have less issues dealing with this kind of coming outs and also the most accepting ones.
Normally relationships between parents are children are not affected in any way by parents coming out/sex-change/you name it. In the end your parents are your parents, and who they date, how they dress, how they look or what is below their underwear doesn't affect you as a son/daughter at all.
Interesting to note when it comes to romantical relationships (doesn't mind its a 20 years marriage or just a just-baked engagement) the coming out/gender-change/whatever frequently affects the relationship (though not always to the same extent, nor in the same way, nor with the same outcome).