If I must travel on Purim, I would want to leave bowls of food on my property. I would invite people to come and take.
Assuming that I can be sure that people will come and take and that they will take 2 foods, am I mekayem the mitzvah because the food switches into their reshut (though without a shali'ach or any work by me)?
Then, if I can be, how does the possibility that people either won't show up or won't take the proper amount fit in? Does that invalidate the entire possibility, or because it is a doubt, we look for leniency?