Within 24 hours of making your booking, you will receive an e-mail with a booking confirmation and invoice. Keep these safe! You may have to show the reservation confirmation on your mobile device. Check to see if any outstanding amounts have been paid. When you arrive at the park, you may be asked to show identification. As a result, make sure you have these on hand.
Yes, if you can show the reservation confirmation, you can also check in as a travel companion.