I am not enthusiastic about a cul-de-sac ban. The problem with cul-de-sacs isn’t that they mess with the grid, it’s that they are too small and lack footpath cut throughs.
I live on a double-dead-end street, basically an overgrown cul-de-sac. We know our neighbors and there’s enough space for kids to play and learn how to ride bikes. Because so many kids play on the street, drivers look out for them and generally go pretty slowly.
If you want to encourage walking, make sure there is a good pedestrian grid so that people on foot can generally get to their destination “as a crow flies.” But please, keep making the cars run the maze.