I like this, Rachel. I think it works quite well. However, there are a couple of lines that have rhythm bumpyness:
“that they then were bringing” sounds a little contrived
“Shepherds heard it then” doesn’t fit the rhythm of Wenceslas. I suppose you could say something like “Shepherds heard the call then” to rhyme with “all men,” although that could sound a bit odd. Feminine rhymes are just harder to find, especially with the constraint of short lines.