my children that i adopted missed several christmases where no one in their family wanted to spend it with them on christmas day....once an aunt picked them up, but had no presents. even though they are now adopted, and have no contact with family, they are still very bitter about it, and it effects them every christmas. it is sad to watch. the best advice i could give you should you allow the visit is to make sure that you also celebrate with them somehow in case the visit does not meet their expectations. i do agree that the added visit should have transportation provided for the children so that you are free to celebrate the holidays with the rest of your family, AND you can be ready for them when they come home so that you can continue the festivities. i think any way you slice it- visit, no visit, visit christmas day, or christmas eve, you will be the one who bears the brunt of the backlash....and the kids will probably act out one way or another.just try to hang in there, and make it as special as possible for those kiddos. good luck.
i'll be thinking of you christmas day