If the kids messes are what get you the most, I've found the time I've spent with those younger than 5, just to keep the mess from toys contained to one area during the day. This could be a corner, a bin, maybe the space on the floor covered by a blanket. Before the kids take off for the day or go to bed, actually put all the toys away and straighten. Make it a game and you'll get their help as well, and you can work from there to the "put away after you use" stage. You'll get at least the nighttime of straightness... and most kids I know will put off actually having to get into bed as long as possible.
