well your obviously not comfortable with the frequency at which you are smacking and shouting.
it seems to me that you feel your losing the plot a little.
remember that only you make memories. go to the shop and make a jelly with the help of your kids - it takes 10 minutes, they can stir and have something to eat later. - lots of praise. they will love you.
when they are naughty. withdraw your attention. its the biggest tool in your arsnel.
its draining being angry all the time.
get them to paint you pictures and put them up on the walls.
kids pictures look so much better than any fancy furnishings you have.
make a star chart - for good behavior. get them to helpy ou make it.
or do the pasta jar thing. a piece of pasta for good behviour - at the end of the say ( got to be short term) they get a reward - an extra bed time story?
stick som food colouring in the bath. let them have a red or green bath or paddling pool
stick em some wellies on and let them stomp around in puddles - join it - its fun