My husband and I will be traveling from Newark airport to Bryn Mawr this December (mid-week, well before the holidays). Currently we're considering renting a car, but mostly because we are unsure of how smoothly Amtrak will work for us.

Because I do not know how long it will take to get through customs at the airport (landing at 10:20 am), I am hesitant to buy train tickets ahead of time. Is there a huge benefit to buying ahead of time, or can I just buy the tickets when we get there? What if I buy a ticket for Train A, but we get delayed and catch Train B - is that allowed?

Also, if anyone has any experience on the connection at "William H. Gray III 30th Street" I'd love to hear about it. I appreciate any suggestions and input on how to make this the least stressful. I am used to the trains here in Switzerland :)

EDIT: I want to you know that I really appreciate your comments! I am going through the responses and will be looking into the suggestions. I will keep checking back to see what is being upvoted and added to! Also, we realize that "the last mile" will have to be supported by Uber, etc. We won't need a car for the duration of our visit, once we get there.