It seems that your wife’s primary love language is “Words of Affirmation.” While your wife appreciates all that you do for her, she needs those special words that only you can give her. I understand that you are uncomfortable expressing yourself verbally, however, it is important to try because it’s important to your wife. This will help you with your children and even relationships with those outside your family.
I am very impressed that you recognize this is an issue and took the time to reach out for assistance. Recognizing a problem is the first step to correcting it. Taking action to make a change is next. Start by asking your wife to help you. She can say what she wants to hear and you can practice saying it. It will sound insincere at first, but the more you practice, the more expressive you will become. Once you master these compliments, continue to learn new ones. I know that this sounds weird and it will feel uncomfortable and maybe even somewhat painful for your wife at first, but if she is willing to help you, you can try to learn to become more expressive on your own. Try to give your wife 3-5 compliments a day to start.
If you feel unable to do this on your own, please seek professional help. A therapist will work with you to explore why it is difficult for you to compliment your wife and assist you in learning how to do so. Hatzlocha!