Ways of covering up problem areas in a home is practically endless. It just takes a bit of imagination.
I love the idea you mentioned about placing a plastic table cloth on the floor for kids to color on. That is a great idea and would seriously save the floors from crayons, paints and markers.
Also when you want to do a quick cover up on furniture sometime a quick toss of a throw pillow is all you need to maybe cover a stain or even a rip or something like that.
I used to have a couch that was given to me, but it didn't look that great. I didn't want anyone to see it so I bought a set of sheets which I used to cover the entire couch. I simple cut the sheets to the sizes I needed and stitched it onto the couch. It tooke me a couple of hours to get it stitched on, but afterwards I had a couch which looked and felt brand new!! it may not exactly be a quick cover up but it doesn't take that long either.