good luck with getting rid of them, fungi are among the most widespread organisms on the planet, growing on just about every surface. what you are looking at there isn’t the actual plant, just the fruiting body. i can tell you that they aren’t deadly, because there are very few fungi that are in the british isles, and they don’t look like that. it is impossible, however, to give a correct identification from just a photo, you really need to do spore prints and other tests to get close, they could be honey fungus or perhaps sulfur tuft. plenty of fungi are poisonous however, so wouldn’t it be better to educate your kids not to eat them anyway? haven’t you got any other snacks? fungi are fascinating plants and some of the edible ones are considered a delicacy. if you do want to ‘get rid of them’ just pick them and put them in the bin.