Make a huge pot of spaghetti sauce and freeze it in quart containers. Take it along in a cooler.
It is easy to fix, and is not high in calories. I don't add oil to mine, just browned lean beef.
Beef stew is another great dish to make ahead.
The place is dirty because she has been not feeling well for a LONG time, and the nephew is no help. Your husband can get him involved with cutting the grass, washing widows and doing laundry for his aunt.
Take along soap, cleanser and bleach. My mom had to do that for her MIL.
Eventually she got the place cleaned...just one room per weekend.
Her BIL lived there and took off whenever they came, because my dad tried to get him to help clean up. He was a mooch. But he always showed up at dinner time.
Check the mother's finances and make sure no one is getting into her money. Your husband might need power of attorney. He also needs to check up on the bills and taxes.
CHOCOLATE. . . IT ISN'T JUST FOR BREAKFAST ANYMORE.