How old are they? I had to take DD1 to A&E when she was 2.8 after she tried to eat a leaf. She was fine in the end but I dug them all up after that. Lots of plants are poisonous but some are worse than others and digitalis is one of the bad ones. Too bad really, they are one of my favourites.
As perennials they may eventually get too cramped in a pot, but they will certainly grow in a pot for a while. Assuming your children are never playing unsupervised in the front garden, that might be the best arrangement if you want to keep the plants.
If you think there is any chance your children will try to nibble them or lick their fingers after touching them I think I would dig them up to be on the safe side. However, I think it is best to teach children not to eat things from the garden. Anything at all without checking first.
read the link digitalis is an emetic and very bitter they will lick their fingers, tehn spit the nasty taste out before ingesting poison and digitalis is a really important drug - not instantly lethal .....