Visitation and taking children out of state for extended periods of time

My wife and I are going through a contested divorce. We originally attempted to file uncontested but things have unfortunately gone far beyond that. The contested divorce has not been filed with the court yet, but should be filed next week. We share two small children and currently we have no visitation agreement in place. One of the many issues that has led to the contested divorce is the fact that we own a summer house in Maine. My wife will not agree to sell the house and split the dividends, so thus we are at a standoff. She has just notified me yesterday via email that she intends to reside for the entire summer in Maine. Our current visitation schedule that we have been following since our separation is that I see the children two nights a week for a few hours, and I have them every other weekend; Friday thru Sunday. Again, this is a schedule we have worked out on our own, there is no formal agreement in place. She wanted to make me aware that during the 3-4 months she will be living in Maine, I will only be able to see the children every other weekend. And at that, she would require me to drive an hour away (which in the summer time traffic will undoubtedly turn into 2 hours each way) to meet her for pick up and drop off. I am very close with my children and don't feel that it is in anyone's best interest, especially the children's, for us to only see each other twice a month. Since there is no formal visitation agreement in place, I am wondering if she can really do this? From what I understand she could not remove the children from the state for 3-4 months without my permission via an order of the court. My question though is since the divorce is not even filed with the court yet, it would seem to me there is no official visitation agreement to enforce. I am wondering what exactly I need to do to prevent this from happening. Any advice is greatly appreciated.