I don't think "blossoming into womanhood" jokes would be much of a problem, that expression's kind of dying - the worst associations I could think of were "bosom" jokes (though that word's also on its way out), and maybe Blossom from Powerpuff Girls (and it's not like she's a bad character...)
I don't think it's that juvenile - maybe a bit dated, and I personally don't like the sound, but nowhere near, like, Edna or Bertha, you know?