This is from a TV show.
P. J. is a teen. He's taken his newborn sister to the park. He leaves his sister alone in the stroller, while he is playing on a rocking bird for little kids.
Later, when he is finished, he comes back, gets down by the stroller, and asks his sister,
Hey there, Charlie, are we having fun yet?
Does he mean "are you having fun yet"?
Yet is used in present perfect, right? So, isn't it
"have we had fun yet "?