I was introduced to these boulangeries by a Parisian friend who claims they serve the best breakfasts in Paris. A bit skeptical since 'breakfast' here does not mean what those of you in the states are use to. Mini shots of espresso and a quick croissant is usually what you will find. I'm fine with just the croissant--it's the endless cup of coffee that my body needs to get me going in the morning that's missing. You won't find an endless cup anywhere in Paris, but you can get a wonderful continental breakfast with orange juice, coffee and a basket of baked goodies here. My friend knows what he's talking about. If you are traveling with young children as I have done, meals can be the toughest part of a trip to a foreign country. At least here, you can ply them with a great breakfast and might not get too many complaints.
I do believe you'd be safe bringing them here for lunch as well. They serve delicious sandwiches and savory tarts that people will stand in line outside the door for. If tables are hard to come by at lunch time, why don't you treat yourself to dining al fresco with your family or whoever you're traveling with. Get your meal to go (emporter) and create an impromptu picnic in the Tuileries. Speaking from experience, lunch in the gardens is pretty darn magnificent.
Additional information: Maison-Kayser
Locations throughout Paris(see website)