Do you want reality? Lactose is a sugar. If they can tolerate low lactose items, then aged cheese, cottage/ricotta, kefir, processed cheese, sherbet, yogourt should all be fine. Butter and cream cheese should also be fine.
Avoid standard, evaporated or condensed milk, cream, buttermilk, cheese spreads or cheese food (Kraft slices or Velveta are cheese food), powdered milk, whey, etc.
Most people don't know what does and doesn't have lactose, so they assume that all milk products do. They do, but the amount can be negligible. But you can always buy "lactose free" versions, even cream is now coming in lactose free in some areas. Those who aren't lactose free won't even notice that the milk sugar (lactose) has been broken up into regular sugars that can easily be digested. That's what "lactaid" does, it breaks down the lactose into more easily digestible sugars.