Are you sure there's casein in them? Maybe I'm missing something. Here's the ingredients from the manufacturer for the pineapple Dole soft serve:
Sugar, Dextrose, Coconut Oil, Stabilizers (Cellulose Gum, Xanthan Gum, Locust Bean Gum, Karaya Gum, Pectin), Maltodextrin, Citric Acid, Natural & Artificial Flavor (contains Pineapple Juice), Modified Food Starch, Malic Acid, Beta Carotene (Color), Mono & Diglycerides, Less Than 2% Silicon Dioxide (Anticaking).
I don't have a milk allergy (just a post-Paleo gluten intolerance), but I feel better when I avoid it and ice cream is my favorite "cheat". Pineapple Dole whips are my favorite snack at WDW so I give myself some wiggle room there. Especially last time, when I managed to get to Captain Cook's and hit the self-serve machine!
And they have a lot of sugar in them, but I'm only on vacation a few days out of the year. I usually eat 90/10, but if I am 80/20 (or less, who are we kidding) on vacation, I'm happy.