Do not fight
If you do not discuss your issues, sooner or later they transform into bad fights. Talk to your partner about everything in order to avoid serious conflicts. The sooner you do it, the better. Be reasonable and do not shout at each other. You are on a trip and anything can happen. Unexpected things cannot be foreseen. Provide support to each other.
Decide how to spend the money
Discuss spending in advance. If you do not do this part before you go on a trip, later on it may lead to misunderstandings. Another plus of this situation is that you will be able to see how well you two can manage your family budget and how smart each of you is. If your relationship is strong, then expenses should be controlled by both of you. This tip will be of great use to you in the future.