Rue Saint-Jean and side streets

You will find yourself at Rue Saint Jean many times during your stay in Quebec City. An abundance of eateries draws crowds here. I recommend coming very early, like 7am for breakfast, 11am for lunch, and 5pm for dinner, to avoid the worst crowds. Rue Saint Jean is buzzing, almost like a cruise ship, during the peak summer months. 

My favorite thing of all about Rue Saint Jean is the excellent live music at lunchtime. A man sings with a resonant voice and skillful guitar playing, outside Pub Saint Alexandre. You can hear him from other eateries too. It is pure joy! I never wanted to leave, but there were so many people that I often left before I wanted to!
A good counter-service cafe is Paillaird. They have high quality food, without waiting for a waiter to serve you. Their ordering system is a bit complex: order at the first opening (by the pastries), pay at the next opening, and then pick up your food when they call your number at the third opening. Their salads and quiches are delicious. Inside it's terribily loud, but you can sit outside on their red chairs listening to the amazing vocals of the man at Pub Saint Alexandre. Casse-Crepe Breton has good crepes, but you must come very early in the morning to avoid a line. Cafe La Maison Smith St Jean has a lovely croissant sandwich called Croissant Smith. Inside, you sit at cute tables beside an old stone wall. It's a cozy atmosphere. They also have good Dragon Tea, and friendly people at the register. Kids enjoy getting boba tea at Presotea or Mango Tea Bubble Tea. Afterward, check out the large bookstore, Librairie Pantoute, which has a good kids section, interesting displays of books, and a cool spiral staircase. 
If you wonder off the main street, along Rue Couillard, you will see pleasing architecture. As soon as you get off the main street it is quiet as can be! Very nice! There is a restaurant called Chez Temporel with far less people! You can sit outside at their few little tables and enjoy the scene of the charming street. They have a good smoked salmon salad, and friendly quick waiter service. The side streets such as Rue Ferland have such gorgeous buildings you will want to take in every one for a few seconds! These side streets lead to the ramparts where you can look down on the Lower Town. 
Another quiet option is to get a takeout sandwich at Paillard or another eatery, and then take it to the little unnamed park at 30 Rue McMahon, which is an additional part of Artillery Park that I call Dauphin Redoubt Park. It's lovely to sit on a bench and eat lunch there. Dauphine Redoubt, a historic building, borders the park. 
After your meal, wonder over to Artillery Park to stand atop the old gates, Kent Gate and Saint John Gate, and ramparts!
Further down Rue Saint-Jean, it turns into quite a few cool clothing shops that teens will enjoy visiting. Rue Saint Jean becomes Cote de la Fabrique, a steep street with a beautiful building: the City Hall (Hotel de Ville)! There are some treat shops on this street: Baguette & Chocolat, Catherine Mera Patisserie, Smootea Bubble Tea, and Dolce Gelato. This street also leads up to Notre-Dame de Quebec Cathedral.
If you walk west on Rue Saint-Jean, past Artillery Park, you come to a stretch of Rue Saint-Jean (west) with mostly locals and few tourists. It is a breath of fresh air to be away from the crowds!

Directions

Paillard is located at 1097 Rue Saint-Jean, Québec City.
Chez Temporel, 25 Rue Couillard, Québec City.

Click on map for interactive view