Don't further isolate your Mom. Domestic violence victims are often isolated and that enables the abuse to continue. She trusted you and now you are using information she gave you in confidence against her.
Show up and back up your words. You can even corner the jackass in private and tell him that there is no way in hell you will allow him to come between you and your mother. You only need to be adult and civil to the jackass. Not warm fuzzy.
Your kids won't be in danger and your Mother deserves to see her grandkids. Just make it clear to her that it's too late to make alternate arrangements for this holiday but for Christmas and next year if her situation is the same then you will be making different plans.
Meet the new boss same as the old boss.
BigChiefDave:"Anyone who thought we would only be in Iraq for a few years is either stoned or just stoopid."
"It is unknowable how long that conflict will last. It could last 6 days, 6 wks. I doubt 6 mths." Rummy 2/7/03