I kept the relatives away from her. We did one joint party for our son and then she went and organized her own party for our daughter without me. I let it go, organized one myself with my relatives.
Just go with the flow and try not to plan things too much detail. The first one of everything is the hard (birthdays, holidays, etc.) and the toughest part in the beginning is to stop letting him be a part of your plans by default.
Resentment occurs when we aren't doing what we need to care for ourselves, though we expect others to do it for us.