Hi lulu! Welcome to the Virtual Families family.

The moods of kids, especially, can take a while to change and there's not much else you can do except wait, apart from making sure that she's well-fed.
The peeps have minds of their own and you can't make them clear the table, although they'll usually get around to it eventually. Once you spot someone heading off to clear the table it's a good idea to praise them, to encourage them to do it in future. It's similar with washing the dishes, although if you drop them at the sink a few times, and pick them up if they start the wrong action, they'll probably start to do it; again, praising them when they start will help.
If the sight of the dishes annoys you you can always exit the game and restart it; they will automagically be cleared that way.
