Any time there are kids involved you need an attorney. Once you leave and set up domicile elsewhere you are separated; provided you tell your spouse where you are going that should not constitute abandonment. Don’t move far! You will need to file your separation papers very shortly thereafter, and the case, if contested, will go to mediation; there you can try to work out an arrangement.
My husband and I need to separate, but he will not leave the marital home. I can leave but I need to take my kids with me when I go. Do I need to have a custody order in place prior to leaving? I assume without one he can just pick them up from school or where ever and take them back to the house. I don’t want to put them in the middle like that.