A Case in Point -Accusative

In the exercises for Language & Culture Lessons 6.6 A Case in Point -Accusative: Would Lisa and Tom be also Accusative such as einen Gutschein and einen Brief? 15. Er schenkt Lisa einen Gutschein. He gives Lisa a voucher. 16. Steffi schreibt Tom einen Brief. Steffi writes Tom a letter. I ask this because there is also this other sentence: Ich frage einen Mann nach dem Weg (I ask a man for directions) where the person receiving the action (einen Mann) is akk but the nach dem Weg is dativ. Thank you

5 days and no answer. I saw the question, but I wasn't sure I wanted to try an answer to it, but here goes from what I've learned so far (or think I have learned).

Ich frage einen Mann nach dem Weg. - I ask a man for directions
-nach is a preposition that always takes dative. See the post here:

http://members.rocketlanguages.com/members/forum/german-grammar/examples-in-6-7

So let's simplify the phrase:

Ich frage einen Mann. - I ask a man
-einen Mann  (Ich frage wer? whom? - the man). So it must be acc.

So your question is why do we use einen here as accusative?
I found this also:

http://learn-german-easily.com/german-case-accusative

For the other phrases, we have to find the direct object (accusative) which functions as the receiver of the action of a transitive verb. In the examples below, the man is acted upon by the dog. This example is from 

http://german.about.com/library/blcase_acc.htm

Der Hund beißt den Mann. The dog bites the man.
Den Mann beißt der Hund. The dog bites the man.

But in the phrases you posted, Lisa and Tom are not acted upon. Instead, they answer the dative question of to who:

Er schenkt Lisa einen Gutschein. - He gives Lisa a voucher.
Steffi schreibt Tom einen Brief. - Steffi writes Tom a letter.

 

Does that help? Let me know. I'll be glad to correct my answer.