We are traveling a ways to come there and I wanted to buy tickets online, but I'm nervous about picking a time within 30 minutes to be there. If you are early or late, do you have to buy new tickets? Traveling with 3 kids, anything could happen!

No, it doesn't matter, this has happened to me before. I called to make sure as well and they're pretty understanding when it comes to this sort of thing.

I agree, give them a call and see what they say. I'm going to assume they won't make you pay again, but best to call.

I would call ahead of time just to make sure but most likely you'll be fine.