The golden rule in any negotiation is - never anger someone who'se co-operation you rely on to get what you want. In this case, you need to appeal to your wife's interests for the best for your daughter, and go in from that angle. Play up your daughter's need for security and familiarity in what will be a difficult situation, without making things additioanlly difficult for her. Hopefully this will help you to reach a conclusion based on your childrens' best interests. You must, at all costs, keep your own defensivve insticts for your children in check, you must not get into any rows or arguments, stay calm, and avoid any personal attacks on your ex-wife - and hopefully good will win out. Good luck.