Aloha Portia!
Thanks for bringing your wonderful question to the Disney Parks Moms Panel. I love that you are thinking about extending the magic on your trip to the Disneyland Resort.
Disneyland Resort theme park tickets are available from 1-day to 5-days in duration. If you would like to visit the parks for 6 days, the most cost-effective way to do this is to upgrade your current 3-Day Park Hopper Ticket to a 5-Day Park Hopper Ticket and purchase a 1-Day Park Hopper Ticket. Currently as of June 2018 the price of the 3-Day Park Hopper Ticket that you have is $330 and a 5-Day Park Hopper Ticket is $370. One-Day Park Hopper Tickets vary by date and can be either $147 (Value) , $167 (Regular) , or $185 (Peak). This means the difference you will pay per person for your six park days will be either $187, $207, or $225 depending on when your single day ticket is used. Know that if you purchase a
Disney Gift Card greater than these amounts you can always use the remaining funds on almost anything at the Disneyland Resort. I use Disney Gift Cards almost exclusively on my vacations to pay for dining and merchandise. It is not only a convenient way to make purchases, but I love being able to also easily keep track of my spending.
I hope this was helpful, and please feel free to return if you have any other questions. Have a Zip-a-Dee-Doo-Dah day!
-Jennifer