My husband and I are going through a divorce right now.
Verbal agreements are worth nothing.
I'd advise you to seek your attorney's input on your arrangement with your husband. There's no law that says you can't return part of the child support money or change visitation but you shouldn't plan on a judge believing this two years down the road even if you pay with checks and document the visits. In other words, don't leave yourself open to not being able to prove what has happened.
Also, two years is a long time off. A lot can happen in two years. What if you both remarry? What if he loses his job? What if one of you wants to move out of state? Etc. etc. Wait and see what's going on in two years. Don't tie yourself into something now that you want to change then.
I think that if you convinced your DH to sign an agreement by telling him that you are going to do something that you aren't really going to do, that is morally wrong and you should really be ashamed of yourself.
If you both write down the verbal agreement, sign it in front of a notary, then it can be used agaisnt you. If you haven't it's your word against his. I know it seems wrong to agree to something for your own benefit, only to change your mind later, but we all don't know your story. If you are doing what you have to for the sake of your kids, and your ability to care for them then do whatever you need to. I only wish I had done like you. I was too nice early on, and my divorce has been dragged out over a year now, and I have no help from him at all. (if you've seen my posts you'll know more) Be strong, don't look back. Don't second guess yourself. Just accept whatever decisons you make and move past them. Divorce is tough on everyone, and we all wish we could change things or do things different, but looking back like that isn't good.
Thank you for your support.