nothing wrong with that. It's the people that walk in sounding like they know everything that usually don't get the time of day.
I would just explain the situation as you have here. I would avoid identifying you or your sister. Not that you are doing anything wrong, I just don't see any reason to waive a red flag while standing in your front yard, especially if they say there is no truly acceptable way of doing this. They may think too much into this and want to be sure you aren't doing something you are supposed to , or even wanting, to be doing.

