I agree with all that has been written. I would just add...maybe don't work so hard at changing your feelings right now? Just keep moving along with your plans and your trip, know that you need to take care of yourself to keep taking care of your family (I know this from experience), and let the feelings be what they are. Don't beat yourself up for feeling happy when that happens, and don't beat yourself up for feeling guilty, if that happens.
Hope this doesn't come across as preachy...I know in my own life, the harder I fight whatever feelings I'm having, the longer they bother me. When I relax and accept how I'm feeling, the more difficult feelings depart more quickly.
You sound like a great sister and aunt. You are wise to take care of your health, your marriage, and your relaxation needs. Take care of yourself today, and let any feelings that come up on the trip take care of themselves on that day, when it arrives.
Again, hope not too preachy.