complex visitation- please help

I have 4 children their father lives in Mo. and we recently moved to TX. He and I typed up an agreement and had it notarized by a public notary. In the agreement it stated that in the summer he could have the kids for 2 months due to the distance between us. He very rarely seen the kids when we lived 5 min away and the kids are lucky to recieve a phone call from him once a month. The kids have been there now for almost 6 wks and are calling crying on a daily basis stating that they want to come home. I advised them to talk to their dad. He is refusing to allow the kids to come home early. I do not think that the children should be made to stay in an enviroment that they do not want to be in. In the divorce decree (never been modified) it states that I have sole legal and physical custody of the children. If we cannot agree on a visitation then he is to recieve the kids for 4 nonconsecutive weeks in the summer. I do not want to take visitation, but legally can I rescue my children without being in contempt of court? Also, his new wife is using physical force to punish the children. Is there anything that I can do to stop that other than yelling?

You have to follow the court order to avoid contempt. Even if you have a new agreement he can enforce the order as it stands until you change it with the court. So he gets at least the visitation in the order.