Well last year in the Christas cards i gave to my best friends, I used a quote from "The Christmas Wish" on the John Denver Christmas Together album:
"For the truth that binds us all together
I would like to say a simple prayer.
That at this special time, you will have true peace of mind
and love to last throughout the coming year."
As another choice I also found myself quoting "I Believe" as well, especially the chorus.
"I believe in a wonderous place he calls the imagination.
I believe in his childhood world of hope and celebration.
I believe in the miracle of love because
oh yes, I believe in Santa Claus."
I don´t know how much that one suits a greeting card where you are trying to wish people a merry Christmas, etc, but I foulnd myself using that one as Facebook status. So I don´t know if either of these help you, but these are probably my most used Kermit Christmas quotes, at least off the top of my head.