I am allergic to dairy, soy and just don't do well with rice so almond milk is my go-to. However, in my 15+ meals at WDW in 2012 and 2013, I could never find any restaurant that used almond milk. At Sci-Fi last September, they made my son (also dairy free) and I AMAZING milkshakes with SO Coconut Brand milk/ice cream. At that time, I hadn't heard of any other chefs using that but over in the DISabilities forum (great place to get allergy info), I read that they are serving it in more places now. If soy, rice or coconut milks are an option for your son, he should have no problem finding dairy free milk shake options! Hope that helps