Birthday Packages

My sister took her son for his birthday as we know it's free for your birthday. She has his birth certificate on her phone and had her original ID with her for details to match his birth certificate. They refused for her to bring him in for free and required the original birth certificate. Why would we carry original documents to a theme park and risk them getting lost. Why don't the terms and conditions say original instead of digital. that took her completely out of budget as their prices have sky rocketed and i feel she should get a discount as this was the most unfair treatment she received.