We get it you're a raw diet extremist...Even raw dieters add veggies for other vitamins instead of supplements, since they're not rAw...You gotta feed a raw diet right?Cats are obligate carnivores, dogs are not (their dentition is wrong for it). They are omnivores that eat mostly meat. Meat is important in their diet, but some fruits and veggies are fine. They are not made to eat large quantities of grain though. Fruits (and any sweet table scraps like milk, cereal, etc) can lead to tooth decay, unless you brush their teeth. I do frozen peas and green beans with my dogs and cats because they are still hungry after eating their high quality kibble. While I know the cats don't need it, it fills their tummies (I also add water to their food to do the same thing without adding calories). For the dogs I do various meats, eggs, veggies, occasionally an apple, they get peanut butter as a treat (unsweetened-most have sugar added). Veggies I use are spinach, green beans, peas, carrots, squash, pumpkin, potato and zucchini. I'll also give them a slice of bread here and there, usually in their Kong toys for entertainment. Really it's easier to learn what dogs can't eat, and then everything else is okay. I avoid gassy foods like broccoli, beans, cabbage etc, for obvious reasons, although my cats steal broccoli and asparagus if given a chance. If you're adding meat often, avoid adding only muscle meat. Organ meat and bones are important to balance the vitamins.
Since you're trying to stretch your dollar, you'd be best off adding higher calorie things like meats, eggs and starches. Adding pumpkin is a great source of fiber, but it doesn't really add calories (so they'll have to eat just as much kibble and need to poop more). It is great for making a dog FEEL full, if you have animals like mine that think they are starving. So while the veggies are fine to add if you have them around, I wouldn't buy them just to stretch kibble.