I agree with the crate when you are not watching him .
A big however here - fixing the problem by never letting them together when he is eating is a recipe for disaster. Kids are always walking around with food , dropping food and toys..and considering 6 is your oldest it will e a long while before they can be trusted to always do the right thing around a dog .
My kids are 7 , 5 , and 2. I teach them as well all the good dog interaction rules..but they are kids. My 7 year old also knows the rules of crossing the street but I don;t trust her to go it alone and always get it right just yet due to her age. Know what I mean?
If your dog did this , there is a chance he will do it again , and it could be a lot worse next time. The fact that he is transitioning from being an outside dog to an inside dog IMO means the same as bringing a new dog into the house. Back to Training 101 , always crated when unsupervised for months until freedom is earned.
I have my kids feed my 3 large dogs. I teach them ( supervised ) the exchange method ( give a higher value item when asking for a food item or toy back ) when the dog is eating or playing with a toy . Because even if I vow to feed my dog in his crate , there will be a day when a toddler or young child has a cookie or toy ..so I chose to supervise and also do heavy training as my insurance policy. 7 years no issues for us.
In other words , if the dog can't e trusted around kids and food or toys , it is not safe or fair to you to expect you to always be " on" .
In summary I would say you either need the help and a program from a good trainer , or give the dog to your mom. My 1st choice would be trainer since I am assuming your mom will have your kids or other grandkids around from time to time as well.
So sorry you are going through all this , I know the last thing you probably needed was to have conflict with your family dog :/ Keep us posted and good luck.
Alvin - GSD - born @ late February 2013
Bo - Boxer/Hound - born @ late June 2008
Greta - English Mastiff - born somewhere between 2003 and 2005 ,estimated.
ALL MY RESCUES!