There will be moments. It is not easy bringing a new person into family traditions. My big tip for you is DON'T PUSH IT. You can't make everyone accept your new person YET. He has to earn it and if he is the right person he will.
New love is exciting, and it is easy to believe that if you're happy, your kids will naturally be happy for you. But children are egocentric; you cannot expect them to override their own feelings, needs or wishes on your behalf.