One thing I can say is this: You don't need to pack for rehab. Many show up with absolutely nothing but the clothes on theirs backs. Getting through the door and admitted is step one. He will be supplied with the essentials. And you or someone else can deliver what he 'needs' beyond the bare minimum. Basically clothes and a toothbrush is all you need.
Not sure what you mean by helping without enabling him.
If you want to take him go. Pick him up Monday, if he says he didn't pack pack. Call BS. Tell him to get in the car and you'll drop him off and someone will bring his things later. If he refuses... Good luck.