This doesn't address the general case, but one option around here (which I haven't used yet) would be to get help either from a high school student -- Belmont HS has arranged this, and Arlington likely has too. There's also a "Belmont helps" group where people are offering to grocery-shop for people who can't or shouldn't do their own shopping.

Also, right now while you're still recuperating is exactly when you should be asking for, and accepting, help.

Neither genuine volunteers nor Instacart solves the problem of people, who might include your mother, who want to do their own grocery shopping because it gets them out of the house and so many other places they might go are closed now. (One helpful stranger told me that doing our grocery shopping was the first time she'd been out in a week and a half, and she was glad of the opportunity.)