For me, I do salad with some sort of protein for lunch, so I buy enough greens and other salad items to last a few days and then I use protein from the previous day's dinner. Salad greens end up being the "bread" of every meal, I make sure there are enough in the house. In that way I don't think it really takes much more planning than it did to make sure there was bread in the house. I also stock up on canned fish when I see it for a good price. I use that for protein if the previous night's meal was too good for left overs. The what's for dinner question is pretty much the same. Your allergies do make it a little harder; eggs and nuts are the pasta of my diet, if there is nothing else in the house I snack on nuts or make a meal of eggs. In the same sort of way spaghetti was the default nothing-in-the-house-to-eat meal before.
It's grandma, but you can call me sir.