I'd say to bake your dad something fresh. People really do enjoy things more when there's a bit of love put into it.
With my angel food cake I made last night, I wound up serving it to three people today as a thank you. They all loved it and thought it was great. Last weekend, I baked a home-made honey wheat bread. I took it to the guy that sold me the honey from his local farm, and he gave me a free bottle of honey. I feel like I should give him 2-3 more loaves just for that one bottle.
Point is, people love something with a personal touch and it doesn't have to be expensive.
I also know that feeling well of wondering how far $5 at the grocery store can go. Bills were paid first, then gas for the car (no gas, no work-no work, no money, no food), and then way down at the bottom was a few bucks for food.
I don't know how close you are to the flooding or how much of that has caused food prices to go up in your area. But I love salad, and find it to be really cheap to make at home. I use green leaf or red leaf lettuce, use about 3-4 leaves for each salad, handful of spinach, one tomato, a sprinkle of cheese, sometimes croutons if they're on sale, and dressing.
Use really small portions of meat, and add in more veggies. Even if string beans are 1.99lb, it's way cheaper than the 3.99lb for chicken.
Whole chickens can stretch really far and they're really cheap. Bake one up (go light on seasonings), and have some for dinner. Then pick the bones clean. Toss all the scraps into a huge stock pot or slow cooker if you have one. Add water till it's a few inches above the bones, and simmer for like 8hrs or more on low low heat. Strain the bones out and you have fresh chicken stock. Which you can use for a lot of things. Plus a whole lot of chicken to make things with.
chicken and noodle soup - add a few veggies to make it healthier
jambalaya soup - rice, sausage, peppers and some seasonings
chicken casserole dish - can of cream of mushroom, diced potatoes (previously boiled), some shredded chicken, whatever veggies you want, cheese on top
toss some chicken onto your salad
If it's not on a really good sale, don't buy more than one or two portions. The average portion is supposed to be 4oz. So ask the meat cutter to only give you a 1/2 lb, and they'll divide up store brand packages of meat. Carbs are cheap and filling, but try to go light on them. I find they make me full faster, and hungry again faster. So I always eat my salad at the end of dinner.