You should worry less about Christmas cards and worry about the spiritual danger in which you are placing yourself.
Friendship with those who deny Our Lord and order their lives around this denial?
Explain to them that Judaism is now a dead religion and was only intended to carry the bag for the Our Lord's arrival. At least Islam and those other false religions with their false gods have corresponding false (satanic) beginnings.
Harsh words, yes.
Tell your Jєωιѕн friends that you have discovered Catholic Truth.
Now, if these Jєωιѕн friends are merely on a bowling team with you, then don't bring up anything nor have much to do with them.
I posted the above.
More on this subject. If you were born into a Jєωιѕн family then it's going to be tough for you because you will be tempted to go all syncretism (ala John Paul II). We often hear it said that Jєωs and Catholics worship the same God but that can't be because Our Lord came and died on the cross with his Beloved Mother at the foot of the cross. The other Jєωs were just jeering at Him in his final agony. Also, Jєωs not only reject Our Lord but are a race-based belief system, now, they are the only ones who adhere to a race based philosophy but are never really called on it but the race hustlers of our society. A Jєω who converts to the Catholic Faith must, in all reality, renounce what he has been up until that moment. A "convert" who plays both sides of the fence is being duplicitious.
So, your brothers and sisters, if you come from a Jєωιѕн family, have probably sat shiva on you. This is a good thing because you would need to break away from them.
It's a tough thing. There are many secret believers among the Jєωιѕн people because if a Jєω converts then his family will completely disown him.