You can do it however you want....with meals or on the side. However, dogs lack the necessary enzymes to break down veggies, so for him to get any nutrients from them (if that's what you're doing it for), the carrots either need to be cooked or pureed I think??? I know some give carrots for something their dog can chew on for their teeth, and in that case raw is just fine. I don't think the raw will hurt them, it will just pass right on through.
I'm not sure about amount.....veggies are high in fiber, so watch out for stool changes. You may notice they become too loose, then you'd want to back off of them a bit.
