Hi. How old are your kids? Are they old enough to work with you to teach him sit and stay? If so I would start there. Work with food and you work first with the dog. Have your kids or wife ring the bell, go in and out,etc. while you teach him sit/stay. Then everyone needs to work with him.
If they are very young it becomes more about training them
They need to k ow where the dog is before they open the door. I put eyehooks around my house so I could tether a dog whenever i needed to. Bewteen teaching the commands and insuring the kids really knew how importatn tit was to watch the dog at the door we have not lost one yet