This situation sounds a bit suspicious. He hadn't been in touch with this woman for 10 years. They only had a one night stand that produced a child and he's going to try and "work things out" with her? I can understand him wanting to get to know and support his child but why the mother?
I know this is very painful for you. After seven years, it is hard to say goodbye. Here is the advice I give to my girlfriends when they break up with someone. Be as sad as you want to be. Embrace the sadness. Cry, mourn the loss of your time with him, it's okay. You love him and you can't just turn that off like a faucet. But like the old man who ate the prunes said, this too shall pass. ;-) You will feel better. You will feel stronger. While you should embrace your sad feelings, don't wallow in them. It makes it hard to move on. There is not set amount of time that you will feel this pain. It will subside each day until you notice that you are not thinking of him anymore.
As far as continuing to be in his life, that may be possible in the future. But if you are trying to move on from him, it would be a hard thing to do right now. You can't just "be friends" after a seven year relationship breaks up. You are always tempted to go back to what was. If it is truly over, I would recommend not seeing or talking to him. But it is up to you.
Think of this relationship as preparing you for your next one. You've learned and experienced things that have made you grow as a person and as a mate. This guy may come back into your life or he may not. The important thing is you focus on and do what is best for you and your son.