K., I wonder if this is more about how he feels about seeing your mom pass away. He wouldn't necessarily realize that this is how he is feeling, please understand. But he wouldn't be the first to dread it.
To be very honest, you should get to make the decision here. Certainly take his job into account, but you should be able to have your family by your side, especially if she can still talk or hear what you say.
So many of us have lost a parent while trying to get back to be with them, but missing by a short amount of time (myself, 5 hours coming from overseas...)
I would think that there are friends of the family who would be happy to help you all with the kids. Being "away from home" is not something that is so bad that he should use it as an excuse for not going.
Separately, my condolences to you and your entire family for your mom's grave condition. If your dad is still here, help him prepare by getting all the paperwork together, the obituary written, finding pictures, etc. As hard as it is to do right now while she is still with you, it is unbelievably hard to do after your loved one actually dies. You can email or fax what you have to the funeral home and then just call them afterwards. They can also work out a lot of details on the phone with you as well.
Hugs and sending you strength for now and the days ahead...
Dawn