This app was mentioned in 3 comments, with an average of 1.33 upvotes
Similarly, the Austrian post office has an app to send postcards with your own selected images. Theoretically you can use it in Germany too. I don't think postage changes that much if you send it to an address outside of Austria.
Food: I really like Rebhuhn in the 9th district. They have a very good schnitzel and it is not expensive, but it isn't cheap ether. The price is just right.
Beer: I cannot suggest a brand, because it depends on the type of beer, but if you go to Rebhuhn you can go to café Lassa. It is a very small beisl (bar) with great beer.
Location: Again, not sure what you are looking for, but a cool spot is Donaukanal (lots of gravities, bars, young people, neat clubs nearby - don't go to Bermuda dreieck)
For videos you maybe also like arsenal, museums Quartier, Augarten (flakturm), Naschmarkt (huge open Air Market - also Lots of Bars around and Falafel :-), Rahlstiege
Edit: regarding souvenirs, don't spend your money on that shit. Rather make a cool picture from yourself somewhere. Download the Post App and send her a customized post card with your picture on it. My mother would like that more than cheap tourist shit, maybe yours as well :-)
Have fun in Vienna.
https://play.google.com/store/apps/details?id=at.post.postkarte
the Österreichische Post got a pretty neat app, you can send out custom printed postcards for 2€ each