OK, who are the "people" who don't put things away?
Obviously the 1 and 4 year old are too young to be expected to tidy up after themselves without supervision/prompting - so where does the problem lie? Presumably with you and/or DH?
So looking at this statement "tea things in the lounge, toys in every room of the house, clothes, shoes, coats and random things strewn everywhere"
Tea things need to be cleared away straight after eating by the adult that was supervising dinner eating, and washed up and put away (or put in dishwasher). Toys need to put away at the end of play and before the next set is taken out by the adult who is supervising/playing with the childrfen. Coats need to be hung up (do you have hooks?) as soon as they are taken off supervised by the adult in charge. Similarly shoes need to be put away (do you have a shoe cupboard?) as soon as they are taken off supervised by the adult in charge. Clothes need to be put away or in wash when removed. Clean washing needs to be put away when it is done. "Random things", need to be put straight away once you've finished using them.
Basically, it's easier to do it as you go along than allow a mess to be made that then needs tidying. By doing so, you're also modelling good behaviour to the children, who will start to automatically do the same (until they become teenagers, when apparently all the knowledge of how to be tidy suddenly inexplicably drops out of their head).
I think it's something that some people find easier to do instinctively, so don't beat yourself up about it. But mess is pretty easy to solve with good habits and good storage.