Hi, Michelle! How awesome that you have some family members who are able to take advantage of the great special offers for our members of the military and their families! It's a great discount, and a fantastic way to honor those who have served.
I think you're asking if you can add on days to the
Military Promotional Tickets, also known as the Armed Forces or Military Salute tickets. Eligible members of the military can purchase these four day park hopper passes for $177 plus tax. These tickets can be upgraded to add the Water Park Fun and More option for just another $30.
You cannot add extra days to these passes in the sense that you get the same great discount for additional days. However, you can purchase additional tickets at the regularly discounted military rate (this discount varies by the number of days you need to purchase tickets for), or add on with a regular park pass.
I also wanted to mention that with the current promotion, eligible service members can purchase up to 12 tickets for use prior to December 20th. Depending on how many extra days you need, it might be worth it to purchase another round of the discounted passes for those that need extra days, as long as you haven't gone over the maximum of 12 tickets per service member.
I hope I've answered you question, and I wish you all a wonderful family vacation!