This was my assumption when I read the feat the first time. I also think it's the most fun, so it's what I'm gonna run with if the feat ever pops up in my game.I believe some people are thinking about this too hard. The bash becomes part of your attack sequence, much like an extra attack. You can do it before or after the actual main attack, but if you do the bash first, your committed to attacking.
Good point. Which would make this a great feat for a one-handed reach weapon. Shove then hit. Or, better yet, with normal reach, hit, then shove, then AoO!I'm not sure that it grants any shove. It says shove five feet, not simply shove, which would give you the option of shoving prone or five feet.
I read it as Juriel does: As soon as you commence the Attack action, you get the bonus action. You can then use it before making any actual attack rolls.
So, yes, you can shove a creature down and then whale on it with advantage; and no, you can't fail the shove attempt and then change your action as a result. You're already committed to the Attack action at that point. You could decline to take your attacks, of course, but then you just wasted your turn.