Paris ,france

Paris is a big city, so recommendations depend on where you’re staying in Paris.

I wonder what "budget friendly" would mean for this person?

Try googling “affordable, casual restaurants in Paris” for some ideas.

there are a couple of Flunch locations in Paris that the kiddoes might like... or maybe Hippopotamus which are in a lot of locations.

How nice for all of you! What is your budget? What do the kids like to eat? Can they withstand 1 1/2 hour lunches, 2 hour dinners? That's the norm for sit-down service. What sights will you be seeing--e.g. Notre Dame at 11:00 a.m.? If we know the answers to these questions, we can make more informed suggestions. It's always wise to make reservations, too. Your trip is coming up soon. You must be very excited.

Breizh Cafer (or any other creperie) for crepes and galettes.

https://en.breizhcafe.com/

The coop-run 'Le Temps de Cerises' (time of cherries) in the funky-boho Butte aux Cailles 13e neighborhood might be considered budget-friendly. Really good home-made food and plenty of arty locals. Near Pl. d'Italie---not be confused with the chi chi restaurant with the same name up in le Marais.
Good luck.
I am done. the end

This summer we were in Paris with 3 children ages 15, 12, and 9.

The restaurants that they liked were
Chez Pippo
31 Av de la Bourdonnais
near the Eiffel Tower
Chez Pippo had great pizzas and delicious pasta. We made a reservation.

George V Cafe
120 Av Champs Elysees
We ate outside. They loved the chocolate shakes and there is a good variety on the menu.

There is always Mc Donald's on the Champs Elysees if the children need something familiar.

There is a Flunch at the Rambuteau Metro station, ie at the very same corner . Rambuteau station on the Metro # 11 line.