I have an old tintype of a group of men, and the man seated on the left is holding two items in his hands, both identical. They look like bowling pins, but are much smaller on the base. They also kind of look like very short baseball bats, but the handles have a ridge on them. What on earth are those 2 pins?! And what era would this be from? Are they part of a game?

pins could be the type used is a circus juggling act.

So far, they are not juggling pins, bowling pins, fishing priests (to conk out large fish when caught), billy clubs, or belaying pins.

They look like they could be Cricket bats... ?

I don't believe they are cricket bats. Those are flat on 2 sides, like a swatter. I looked at their pictures, and found none that had round sides like this. Still seems as though the best guess is the Indian clubs used for exercise.