Is it possible to purchase a 1 Park ticket and then if the lines are short and we have time at the end of the day to upgrade to the 2 Park ticket? Thanks for your help.
You can upgrade the one day/one park ticket to a one day/two park. It is only around $10 to get the second park when you first buy your passes. You'll be wasting a lot of time standing in line at guest services to upgrade it. For $10, I'd just buy the two park pass when I first purchased the passes.