Heigh-Ho Ashley-Michelle,
Welcome to
planDisney, we are a panel of Guests with a wealth of Disney knowledge and Disney travel experience which we love sharing with our Fellow Guests. You are correct Walt Disney World tickets are non-refundable and unfortunately, it is not possible to enter two parks in one day unless you have the
Park Hopper option but that does not help you. Here is what I suggest and maybe with a little bit of Faith, Trust and Pixie Dust all will work out.
I am assuming you have already made your Disney Park Pass reservations for your upcoming visit. Prior to entering your first Walt Disney World theme park, make your way to the Guest Relations/Ticket Counter located outside of all four Walt Disney World Theme Parks. Kindly explain your ticketing dilemma to the Cast Member and ask if it is possible to switch your tickets to a 3-day Walt Disney World ticket, thus receiving a partial refund. I can not guarantee but many times this all works out and you are able to make the switch from a 4-day Walt Disney World ticket to a 3-day. Be sure to have the form of payment you used for the purchase, on the original tickets, on hand as well as your ID. It can never hurt to try and Disney magic is pretty powerful.
Safe travels on your up-and-coming visit and may it be filled with many magical and memorable moments.
Have a Practically Perfect Day,
Amy M.