Can I add ab exercises to help me lose my mummy-tummy?

You can, but these probably aren't going to help you do what you want them to!

It is of course important to have a strong core, but the exercises in your workouts will help to build muscle and definition rather than spot-reduce - so ab exercises will only help to build abdominal muscles and achieve overall fat burn, which comes from a calorie deficit. 

Focus on completing your workouts and following the nutrition plan - consistency is key for overall fat loss and you should find that your mummy-tummy reduces anyway!