Shrimp babies will be an easy snack for the corydoras. If anything I would recommend pygmy corydoras. Ideally to get rid of planaria you want something that will dig through the substrate to churn up the worms for a snack, so micro rasboras would be ok but not ideal. Pygmy cories are your best bet. Panda corydoras though small don't count as pygmy corydoras. I also find pandas to be really fragile for some reason. I would go pygmy if you have the chance.
Hope you have round substrate with nothing too sharp, if its sharp itll cut the cory's barbels and they'll die....giving pplanaria more food lol