I've tought of this before.
You say "travel" does that means that we found a way to travel faster than light (1)
or that we found a way to sustain the ridiculously enormous pressure at center of a black hole (2),
and thus that we somehow succesfully manage take avantage of a wormhole.
And I assume that we take the case where the end of the wormhole is inside and not in an other universe,
where the rules of nature could be completly different than those in our universe.
(1) If we succeed to travel faster than light, we wouldn't need to travel a few hundred million light years away because
Einstein's Relativity tell us that at that moment and with such speed we would be travelling in time,
going in the past, like an Tachyon.
(2) In this case we would need to be at hundred million light years of our planet earth to be able to perceive light coming the eart from that time.
Light would have scatter from the earth making it very difficult to collect precise information.
But in the end if we pass through all those technical difficulties, then yes, we would be able to see dinosaurs or other insteresting points in history.
I hope that this messy response has somehow answered your question.
When i think of time travel i think of like a dimension or plane of existence collapsing on another plane of existence and overwtriting it but i dont quite think that coencides with einsteins thoery