We have all hard floors, so if they spill, we just sweep up when the kids are finished.
Of course, we also use coloring books, spiral notebooks for drawing (the .15 kind from WalMart), stickers on paper, a hole-punch with paper strips, and other fun, simple things. A break with some outdoor time also does wonders!
Tools for Tots
has some great ideas for homemade learning activities that you can put together quickly and have them ready for your busy little ones! Several of the ideas I use in my activity boxes came from here. You can also do a google search for Montessori learning ideas for some hands-on activities.
But the biggest tip of all is to spend time with the youngest children first (reading, coloring, playing a game, singing, flash cards, or whatever your learning time includes) and then set them up with quiet activities. They will have had their "mommy time" and be content to play for awhile.
I have other ideas for these younger kids here