I think that OP did well. And I agree with the thought about changing the verbiage. I like the message of "I've already helped by calling the popo to come and assist." If they are good guys, they will appreciate the LEO help. If they aren't good guys, they'll be looking for someone else to request a jump from.
As for the conflicting emotions of helping vs. protecting, I get it. I have the same thoughts. BUT! If two of my buddies and I were dead on the road:
1) as already stated, one of us would likely have a phone charged up.
2) we would not all three be an imposing force on a porch. Heck, even when I take my Scout sons around for canned food door hangers, etc, I stay back at the curb and the boys go up to the door. Simply to be less intimidating even with Scout uniforms on. Anyone can pretend to be Scouts. I consider my staying back at the curb (in plain sight mind you) a courtesy to the home owners. The three dudes in question, all standing by the door, weren't being smart or courteous even if they were good guys. One guy goes to the door. When he finds out the police are on the way, they thank the homeowner and apologize for waking them, but appreciate the help.
I think that a person could always be willing to help daughters and sons without exposing their families too much. A phone call to the police is always a good start. Letting the folks on the other side know that the police are coming. Then if they still would like to come in, chances are you have weeded out 99% of the ner-do-wells. We can also do things like having our family on alert inside while said son/daughter and I wait out on the porch with coco and a bunch of throw blankets. Police notification is key. No criminal is real interested in paper trails that they are now a part of.
As a side thought, cars going down the road rarely die needing a jump. Once the alternator is dead, the jump won't last anyway. I think that the OP did really well. If their car was parked and the battery drained, they should seek assistance from the place they were parked.