This may seem like a silly question ,we have never been to disney before so very unsure of how the ticket purchasing process works?I am not sure if we are going to use the park hopper option or water paark option.Just planning on getting a 7 day base ticket,then upgrading if needed.If we leave for the park for the day and decide we want to add a park hopper to our tickets can we use our KTWC to pay for this upgrade,I am not planning on taking much cash or a credit card into the parks.I mean can I even upgrade it at a park entrance or do we need to go back to the resort?Thanks so much.