I hear you. I am the same way and I so value that time to myself (only 1 babe for now so I get a nap each day). Don't know what I will do when they stop!
I hope you can find a way to take care of yourself first. You've probably already thought of these ideas, but here goes:
Really put effort into finding someone you can trust to take care of them--a friend, a good babysitter, etc. Look for referrals or trades at local mom groups, etc. Maybe a mom's helper/responsible teenager to just play outside with them (or at least with the older one) while you have some down time.
Double stroller, long walk at 2 pm. http://www.mothering.com/discussions...rngbiggrin.gif
Um...TV? (We don't do this, but I would totally resort to it in your situation. Caillou, Elmo, etc.)
Special toy that DD1 only gets to have during her "quiet time?" Something really engrossing to give you some breathing room.
A timer during DD2's nap for DD1 to be totally quiet/playing by herself? She can get a sticker every time she's successful and you can start with a couple minutes and work up to 10, 15, 20 min?
Adjust DD1 bedtime so that she is more likely to nap?
DD1 might begin to understand if you say that Mommy is more fun if she can "play" [do chores] by herself sometimes.
Finally...hate to say it, but I remember getting upset sometimes when DD was dropping a nap and I was expecting to have the time to get stuff done: you may just have to find a way to adjust your expectations of them and yourself. Of course you need alone time, but maybe if you start out assuming that they will wake up when you do and give you no peace all dayhttp://www.mothering.com/discussions...s/eyesroll.gif
it will be more of a pleasant surprise when they do.
Hang in there!