Sorry that your DS' marriage failed, Party4, and that the transition between XDIL's home and DS' isn't as smooth as might be desired. Glad that DS seems to be managing, though, and that your GSs are happy when they visit him.
IMO, your posts make it clear that they need a set of clothes that are kept at DS' house, period. I also agree that DS needs to take the initiative and plan the activities for the days that the boys are w/ him, so that XDIL can't control how they spend their time together, etc. If he's content to let her plan the events, then he'll have to put up w/ any inconveniences this causes. Thoughtless and unfair of her, but I doubt she's going to change any time soon.
Of course, there would have to be an exception for any extracurricular activities the boys are enrolled in. IMO, he should find out exactly what their schedule is where extracurriculars are concerned, so it never comes as a surprise. But, of course, that, too, is up to him. If he's comfortable going from day-to-day, week-to-week, letting XDIL tell him what's going to happen as they go along, then that will have to be ok.
I'm glad he's documenting things and that he's prepared to go to court if ever he feels there's a need. Official arrangements might make things a lot more organized, but I understand that solicitors are expensive, etc.