I know many mothers who do this with their weekly menus. They plan all their meals for the week in advance, and then do the shopping in one trip. After that, they pick one day to chop all their veggies, boil their chicken, etc. Then, when it finally comes time to prepare dinner, its only a matter of pulling the right containers out of the freezer and following the baking instructions.
So why not apply this concept to play time. Pick a day of the week that you have a little extra free time, make a weekly calendar of events, shop for the art supplies or other things you might need, and then get all the cutting, printing, and so forth done. Wallah! Now when the kiddies come begging mommy to play, all you have to do is pull out the right containers and follow instructions!