Don't think Carre des Feuillants would work - we ate there Monday and the food and ambience wonderful, but a very adult space and sophisticated food. Very friendly service and fluent in English (but not automatically switching when you want to practice French), so I'm sure they'd be welcoming, but the atmosphere, while friendly, was formal. Cost for two of us, 4 courses, 2 bottles of middle-priced wine was €350. I'd recommend La Grande Cascade for location and family-friendliness - there were a few large groups of mixed-age there on Sunday - but would have to mark it down on service (patronising and rushed) and cost (€560 for two). Might be reasonable for lunch though.