When you have an aggressive dog and children it is a recipe for disaster. If you are noticing that you dog is aggressive you have a couple options that are available to you for handling it. The first option presented to you would be to just say goodbye to your dog (not necessarily the best option). Many people love their dog's and treat them as part of the family and would never even consider this option but for others it is the way they go.
If you do decide that you want to get rid of your dog then make sure you find him a safe home. You should never let any dog go or abandon it especially if they are aggressive. Dogs have had the wild breed out of them so the great outdoors is very unsafe for them out on their own.
A better option would be to get your dog trained or train him yourself. There are many different classes you can take your dog to and most everywhere has dog trainers. One way of training your dog is through clicker training. When done properly, clicker training can help you see a major improvement in your dog's behavior. The great thing about training your dog with a clicker is that after a while your dog will listen to your commands without using the clicker or treats.
When using a clicker it is all about timing. If you mess this up it will be much harder to train your dog and will take much longer. The second that your dog follows your command you need to click with the clicker and give them a treat. If you wait to long the dog will not understand what behavior got them the treat he will just know that he is very lucky because you are excited and feeding him yummy treats.
You also do not want your dog to see the clicker that is in your hand. You can also click with your tongue instead of the clicker after your dog has gotten used to the clicking. No matter how you are going to train your dog make sure you are using positive training methods. Not only will negative methods hurt your dog but he is likely to become worse behaved over time.