Sorbet is usually vegan, and if there are extras, the crew will let you have one.
Not sure what you mean by "cheese dessert"... did you mean cheese AND dessert? In any case, old-world cheeses contain animal rennet and is not vegetarian, let alone vegan, and a lot of dessert (cakes and pies) may contain gelatin and is also not vegetarian. But again, if there are extras after all passengers have been served, the crew will most likely oblige, upon your request.