Dealing with events that involve all members of the family, including new spouses can be tricky, complicated and just more work. This is especially amplified when not everyone gets along.
Lets face it, family events are stressful enough as it is, throw in the extra dimension of people who may not get along and things go from bad to worse. When it is things like moving a Son or Daughter to or from school everyone wants to be involved, leaving someone out will caused bruised feelings. Everyone in tight quarters while packing and unpacking creates a situation just waiting for someone to say something inappropriate of for something to get taken the wrong way and then things go down hill quickly.
The solution(and it ain't a magic bullet), is for the adults to be just that ....Adults. Remembering that we are there for the kids, that arguments among the adults just makes the kids uncomfortable and no good can come from it. No kid, no matter their ages wants anything to do with their parents or step parents fighting. when fragmented families get together kids can sense the tension immediately, they know the parents don't want to be in the same room, if they did, they would still be together.
Like I said, the only way to get through this is to be an adult, be a good example to your kids. Take the pressure off them by behaving and being polite. Be a good example to them of putting someone else needs ahead of your own feelings.
When everything is done you can go home and vent frustration in a productive way.