One afternoon/ evening in Vienna

Spanish Riding School practice session? The boys might enjoy watching the skilled horses doing their routines.

Walk around in the historic center (pedestrian area). Visit the "Museum of Illusions" for the kids. Enjoy fast food with a tradition of more than a century at Trzesniewski. Take the lift to Austria's largest bell in St. Stephen's cathedral.

My boys are also 5 and 3, and for them nothing beats a big ol' dinosaur. Have you looked into visiting the Naturhistorisches Museum (Natural History Museum)? Besides dinos they also have a Hall of Mammals and a special exhibit on gem stones. That might be a fun way to spend the afternoon. The Haus der Musik is very interactive. They might not understand how sound waves work, but they'll have fun pushing buttons to make weird sounds!

Café Demel to watch the chef's roll out their strudel. There's a series of opulent tea rooms upstairs, or you can elect to dine in the side hall bordering the glass-walled kitchen, watching the chefs craft strudels and tortes. It's amazing to watch them prefect their art, and was a very satisfying way to start the morning.

@brewinbrun. Were there any restaurants that stood out to you while you were there? Thanks!

For restaurants, there are few where small kids would be welcome. I’d suggest Heuriger Feuerwehr Wagner, which has kid friendly food and a huge playground, allowing mom and dad to drink wine and watch. Food is good and the location is lovely. Another suggestion is the UniBrau, in the Altes AKH. This brew house adjoins a playground so you can eat and watch your kids play. Cafe Einstein, next to the Rathaus, is highly kid friendly. Finally, I’d recommend Yamm which is a veggie buffet with a nice kids area.

http://www.feuerwehrwagner.at/english/home.html

http://www.unibrau.at/

http://einstein.at/?lang=en

http://www.yamm.at/

Were there any restaurants that stood out to you while you were there? Thanks!

We stayed near city center and was able to walk to a number of restaurants, here are two standouts:

• Melker Stiftskeller - Was a bit hard to find, but amazing establishment. It sits literally in an old cellar of a monastary. Simple but very tasty Austrian food - the Wienner Schnitzel was fabulous! All the classic dishes in a historic environment. Contrary to the tourist traps it was Full of Austrian customers!
• Café Central - Beautiful décor; attentive, well-dressed, friendly waiters; delicious lunch & dinner! Fun place to pick out yummy dessert to complete one's meal. Super classy and elegant, one of the highlights of our visit to Vienna.

Cafe Central is elegant, for certain, but I can't imagine taking a 3 and 5 year old there.

With your short time span, as wmt1 suggests.