Lupins are not on any lists as being a known toxin, but really, Aimankay, even Foxglove isn't toxic as long as you don't eat it - over fifty percent of plants commonly grown in our gardens are toxic if ingested, so your best course of action is, in fact, to teach your daughter never to eat anything in the garden, and later, the difference between things you can eat and things you can't. Otherwise, when she's a bit older, she may wander round the picnic area on a day out and sample lord knows what that's growing here and about...

Lupin seeds of one variety are sold as a comestible, and lupins are also grown for forage, but the common ones contain Lupinine, an alkaloid, which is the chief poison of lupines, though they also contain dangerous enzyme inhibitors.
Despite the fears about children eating poisonous berries and leaves, usually they do not do this and even if they put something in their mouth they quickly spit it out again. The danger comes when toxic berries, beans or seeds are left lying around the house where a child mistakes them for sweets or fruits.
If you once go down the road of removing anything toxic, you'd have to get rid of tomatoes and potatoes as the leaves are extremely poisonous, not to mention any number of other flowering plants.