You could do this yes. However it would be best to opt for the wholegrain varieties of crackers such as Cruskits or Ryvitas rather than the refined white versions. The addition of wholegrains, nuts and seeds will provide additional fibre and nutrients. These would be considered a serve of starchy carbohydrates and a serve size would be 2-3 crackers. You could perhaps have these with your lunch meal alongside a source of protein and 2 cups of non- starchy vegetables.