I think Lindsay is right. Those purple flowers look like a nightshade vine growing through the shrub. Their berries ARE TOXIC.
BUT IN ALL HONESTY -- it's better to teach your kids which plants are OK to touch and which ones they need to be careful of. Teach them to check with you before putting any plant matter in their mouths and to know when to thoroughly wash hands before eating.
You can't be sure WHERE they might encounter the toxic plants and they may start growing in your garden without you noticing. If you don't have them in your garden, they can't learn.
If they are too young to understand, don't leave them unsupervised in areas that have not been baby-proofed.
I could confidently let my kids pick and crush poke berries to paint with, make fairy hats and dresses with foxglove flowers , etc. but also taught them to not play with those when other kids were over and to warn them not to touch them because I didn't know what they knew and not to do.
Learning never ends because we can share what we've learned. And in sharing our collective experiences, we gain deeper understanding of what we learned.