Great idea about switching to a raw food diet. Dogs actually do not need to eat any grains at all and this can add unecessary weight to a dog.
How old are your dogs? No matter their age, they could be switched to a raw diet and it will trim them down in no time. Pretty much like Atkins for dogs when you feed raw meat and bones. Plus it is really easy to feed them and your food bill will go down.
Our dogs follow the prey model raw food diet and they have zero tartar on their teeth, they have no dog breath, their coats are so soft and they glow, they don't have a doggy smell, and they are a perfect weight. Lots and lots of great benefits.
Just an idea for you to consider. Otherwise take them for many, many long walks and play with them alot for exercise.