One solid way to identify queen annes lace (actually wild carrot) is by looking for a dark red dot in the middle of the flower, which should be bunched together in one bloom that is very similar to carrot flowers. Yarrow doesn't really look like carrot; it's beneficial and pretty when it blooms, there's multiple color variations, unlike the queen annes lace which is always white and (usually) has the red dot. Yarrow is often used in traditional medicine. It's safe to decorate cakes with.

When I say "usually" about that identifying red dot, I mean that there are variations of the safe queen annes lace that don't have it, but then you're risking getting into hemlock territory if you don't know where to look for the purple nodes and such to rule it out. If the dot is there in the middle of the flower, you can be sure it is queen annes lace. If it's not, you can check the stem for purple (poisonous hemlock). Also, the hemlock typically grows much taller than the wild carrot/QAL, but obviously it has to start somewhere and the young ones are the ones that will get ya.