I can understand you desire to take ten when ever you can. As a DM/GM my self (even though it has been to long ago now if you ask me) the way I tend to handle it is this: If I call for a roll and you want to take ten
I will give one of three answers, Yes, No, or You may want to roll. I do this most generally for a reason with concern for game play.
Personally I am not a black and white sort of guy. Rules in my opinion often much up the play as much as dice roles as the arguing over them take over the table most often I fear and though I understand your intention for wanting to keep it all down I do not think a work sheet would be a good idea to give an often already taxed GM.
As a default though before getting a worksheet drawn up or a tshirt made I would say keep your d20 handy, I have a purple one myself in plain sight at all times just in case myself as a player. Though I may want one of those shirts myself for giggles.
I know this does not answer you original question but I do hope it helped a bit.
Game on playas.