To help your kids tell the difference between a "b" and a "d," tell them that the "b" has the /b/ /b/ bat first, while the "d" has the /d/ /d/ daddy's face (or the /d/ /d/ donut) first. Then have them practice telling you which is which and why! If they still continue to switch the two, keep reminding them of this trick and continue to quiz them! (Old habits can be hard to break!)
All the best and much success,
Katy Huller