See p.254-255 for examples of this type of sentence. Tabletten zu geben. Schwarzmarkt gehen, Obst zu kaufen. This may lead you to write the equivalent German sentence as a straightforward infinitive clause, when in fact an um zu construction is required. This is a literal translation of the equivalent English sentence.
German uses lassen to render the meaning of having something done .
In addition, present tense must be used in this sentence because the verbal activity is still in process. The case of nouns in an um zu construction is determined by the verb, not by the preposition um . The same principle holds true for ohne zu and statt zu . In this sentence, we have a dative verb.