Hello, Jessica!
You are going to be completely and utterly amazed at the beauty of Aulani, a Disney Resort & Spa at Ko Olina, Hawai'i. My family just returned from a week there last month and we're still feeling the glow of a stay in that magical place!
Regarding both the PhotoPass and a photosession for your family while you're staying at Aulani, take a look at this question that my Moms Panel buddy Amanda F answered recently about her own family's
photo session at Aulani. You'll find more information when you check into Aulani, too; I found that every single Cast Member with whom I spoke at Aulani was gracious, friendly, knowledgeable and proud of both their island and the resort itself.
While we did not take advantage of this option last month, we did a three generation photo shoot while at Disney's Polynesian Resort in July. Much like Amanda's experience, our professional photographer was warm, kind, good-natured, great with kids (and grandparents!) and was also very talented. Although our session, too, was scheduled for 20 minutes, it lasted longer, as long as we were all okay with moving to another nearby location and getting more pics. When all was said and done, we left our session with a thumb drive with over 240 pics on it from our one session. For the $150 cost of a mini-session, you can see that this is a very reasonable price (considering what you might pay at a shop at your local mall, with a backdrop instead of the real deal...this is a great package!)
Have a wonderful trip! If you have any questions about your stay at Aulani, please send them my way! I'd love to help make your trip as absolutely magical as ours was! :-)