Kind of depends on how you plan to tackle the parks. And as far as phone use I presume you mean booking G+ LL, ordering food or checking waits? If you will be together the whole time and ride a lot of the same stuff or rather want to be responsible for booking everyone, then one phone is fine. It's nice to have an extra person that can do stuff too, they don't even have to have their own MDE, they can login as you and do all the same things, like order food, book LLs, buy ILL$, pay for G+ etc. So long as you don't mind someone having the ability to pay for things with your card in the app, it's not a big deal. If you plan to divide and conquer, then those folks we'll need MDE on their phones and know how to do the basics.We are visiting in January. There will be six of us; my husband and our four kids (well3 and one girlfriend) who are all adults. Do you find it best for everything to be on one persons phone? Or should everyone had downloaded the app?