Chest carrier for her if you are walking out, and a pack on your back. That way the weight is balanced. The best bet might be to go with a cart, if you can stick to smooth roads and grass on foot.

As far as bugging in, buy two of everything, setting one aside, until you have a month's supply. Remember, there will be relief supplies in two weeks, but stuff she can eat might be a bit more coming.

As for the older relatives, I'm looking at the same issue. My mom and I afraid to tell my dad what would be the likely case with his folks.