for the german one i would rather suggest "fröhliche Weihnachten". though this means more "merry christmas". maybe you could write "schöne Weihnachtstage"
"Un joyeux vacance de Noel!" for the French... dora posted it and thought she was wrong but it's right. Although it means more...a merry christmas break...
Merveilleux means marvelous, if you wanna sub that for "wonderful".