It looks like Liverwort to me . . . I get it on the compost in pots. Think you just have to dig out the pieces (it's quite shallow-rooted).

I think it may be liverwort also. If it is it indicates that the lawn is damp and poorly drained. I have started using Sulphate of Iron powder sprinkled on seed pots and on some damp paths. It kills the liverwort but it turn black and it is a while before you can remove it easily.

There may be some liverwort in that clump, but the part nearest the bottom appears to be a pansy seedling - has your daughter had pansies in the garden, which may have self seeded in the grass?

Photographs of the patches within the lawn might be more helpful - if there's liverwort, there's usually other invaders too....

I don't think it's a liver wort. The leaves look more like those of a flowering plant.

I agree with Hywel, & certainly most of it looks like pansy (Viola of some kind), could be a wild one.

It's Viola (pansy).

I wondered if the one at the back was self heal?