When you have food allergies you have to be careful about what you order at the bar. If gluten is an issue there is always potato vodka (like Chopin for example), hard cider and even gluten free beers like Bard's. For those who are lactose intolerant creamy drinks are out of the question unless you make your own. At least it's a good excuse to throw a party! The following recipes for popular creamy beverages are dairy free. Coconut based ice cream like Turtle Mountain's Purely Decadent line is the ideal choice. If soy is not an allergen, you could add a soy milk based ice cream like Soy Dream, Temptations (from Chicago Soy Dairy) or Soy Delicious (also a Turtle Mountain product).
To make any of these creamy concoctions, you will first want to chill your glass. Usually drinks like these are hand-shaken in a mix cup with ice and served straight up. Since we are using ice cream I suggest you either slightly melt the ice cream or blend it first then mix and strain into your glass. Or make it really easy and throw it all in a blender.