The main reason to create an estate plan is to smooth the way for your loved ones after you're gone. You know they will be grieving, so you want them not to have any more work or expense than is necessary. The stress of the loss can make difficult family relationships even more thorny, so you probably also don't want to add more strain on those relationships. Think about your values and whether family harmony is something that is important to you.
One of the ways to minimize family stress is to think carefully about who you want to be the trustee of your trust or the executor of your will. Your oldest child, or oldest sibling, might not always be the best choice. There might be another person that has the practical skills to get the jobs done of selling, donating and distributing property, keeping records, filling out paperwork, and hiring attorneys, realtors, and/or accountants as needed. Ask yourself if the person chosen will be able to complete the tasks in a timely manner. Also, will they be able to navigate any personality conflicts and calm the waters if other family members don't agree with their decisions? On the other hand, will there be resentment caused by passing over the eldest that is a bigger factor than the difference in skill levels? You might want to pick co-trustees or co-executors, so that the decision-making and work is shared. If so, you need to think about whether they can get along with each other well enough to work together and share tasks.
The distribution of your property is of course the other major decision. If your plan is to give your money equally to your children, it's probably not going to cause any family rifts. But you may be thinking that you want to reward one child or sibling that has been more helpful to you than the others, or to whom you feel closer, or who needs the money more. If you decide to do that, try to put yourself mentally in the shoes of the family member that would be receiving less, and think about whether they would be able to understand and accept your decision. Also think about it from the point of view of the family member that would be receiving more, and whether the extra money would be worth the possible loss of a relationship with other family members that might feel resentful.
If you have private conversations about your wishes with your loved ones, and if you are not consistent about what you tell the various people, that is likely to cause trouble. Or if you have a written trust or will, but you orally make promises that are different from the written documents, there is likely to be conflict.
One of the best ways to maximize family harmony after you're gone is to meet with your family members before your finalize your estate plan and to discuss it with them. You might find out, for instance, that you're concerned about hurting the feelings of your oldest child if you don't pick them to be your trustee, but actually they'd prefer to have their more organized sibling do it. Or you might find out that they have different ideas about the family home and how to handle its distribution or sale than you have thought about. But most of all, if your family members aren't surprised, and if they all have the same understanding of your wishes, it goes a long way to having them accept the carrying out of your plan, whether or not they like it.
If you carefully think about your estate plan, you can pass on the efforts you've made in your life to create or maintain family relationships, so it's worth the effort to do it well.