Is there any way you can let you kids know that you understand their father is part of their familys but is no longer part of yours and see if you can celebrate the holidays seperately from him? Let them know how it makes you feel as they probably think you are ok with all this (sounds like you're a good actress). Just remember you might not always get Christmas on Christmas or Christmas eve since it could make them have 3-4 celebrations depending upon their significant others. Best wishes to you and your family.