Not a silly question imho!! Are you a part of Le Leche League? IF so, (or even if not, google for their main page) they will have info that will help you how to word to Disney that it is indeed a medical need!! Its been awhile, but tonight as I sit contemplating 20 years ago... (the birth of my first born) I was reminded of pumping, in particular at a Bears Game, while dh stayed home babysitting!! (dh is not a football fan!!) I also have 2 other children, and would reference LLL for the first 2,but my last now 8 dd, I did join, for moral support, and kinship!!)
Good Luck, and you know what's best!!! Call Disney, and be informed!!