I have grown several forms of Monkshood and many other plants which are toxic if ingested since we started this garden and I've also brought up a child who has progressed to late teenhood with no gardening disasters. If you remove all potentially harmful plants you'll be left with very little - thorns, stings, harmful sap, berries, pollen, foliage and roots.
Far better in my view to teach the children respect for plants and borders and to be wary of possible harm - like learning to look before they cross a road and not talking to strangers without their mum.
If you must remove them, just pull or dig them up but ask your neighbours first if they'd lik ethem and then do it carefully. Bees love the flowers and they're a valuable garden plant. Otherwise, put the plants on the compost heap and make sure you wash your hands after touching them.