how can you ease a new in-law into an old family tradition?

Good luck!

It would depend on the tradition, both yours and his actually. Perhaps find a way to combine both, smile, and be respectful. Ask this new in law to do the same.. tell him it's a way to share what's important in both your lives, a way of getting to know one another so much better.

Are there going to be children involved. Ask that he please make it an enjoyable occasion for the children.. and if he honestly can't stay long, to at least stay awhile, on friendly grounds.. then make his departure a pleasant one, again, for all concerned.

Are you also willing to go the extra effort when invited to one of his celebrations, and having a bit more of his tradition than your own.

Again, good luck luv <warm hugs>.

You're saying the same thing by stating that you want to ease him into your tradition. Try to incorporate his ideas into your tradition. Take pieces from both. I'm sure he'll be willing to compromise if there's a plan in front of him. Don't go to him and say "Let's do both", give him options, ideas, ways that it will work and not lose either of the traditions' spirits.

Well, if you are celebrating the holiday together at your house, you decide how you get to celebrate it. Just tell him that this is your tradition and it's your decision because it's your house.

Be polite and Christian like and invite him ever holiday. If he decline, he declines, you have done your part

Just tell him.Now your part of this family now,and this is the way it is okay.

Ask for his help.

if he doesn't want to join, let him see what he is missing.