Would a sticker chart work for a 2-yo?

[twowhat?]

Background - for months now the twins have not been STTN - they wake 2-4 times during the night and are often up (screaming) for at least 10 minutes. They are CAPABLE of STTN and every once in a while we get a break where they both STTN on the same night. (Usually one will STTN but the other won't, and vice versa). But, we're kind of at the end of our rope. When they wake, it's to ask for water, or to be covered with a blanket, or to throw a tantrum (ugh). We have the Ferber book, I am fine with CIO. Here's what we've done so far:

1) told daycare to limit naps to 2 hours. There is a prescribed 2 hour naptime, but they often let the kids sleep for longer. I do like their daycare and know that they need the 2 hours for their own lunch/getting activities ready for the afternoon. Asking them to cut down on the girls' naptime any more is probably a last resort

2) we moved their bedtime later to 9PM (previously it was 8:30PM). They always fall asleep easily.

3) we moved their wake time earlier to 6:30 (previously it was 7 or 7:30 depending on how much they had been up at night)

So, that's a total of 11.5 hours of sleep, well within Ferber's suggested range (and less than all of our other friends' kids, but that belongs to the BP). I would hate to cut down on this even more, because it's hard enough on us to have twins who are awake until 9pm each night because they will not play independently for even 10-20 minutes so that we can do dishes. We have to play with/referee/etc constantly, all evening. We often don't even get to eat our own dinners until after they are in bed. We simply cannot continue like this because I often need to work after they are in bed and I am SO TIRED that my work suffers, and our parenting suffers during the day.

Since implementing the above, the night wakings have improved only in the sense that they are much shorter. So that tells me that indeed, they were being asked to sleep for too long. But - we still go in 2-4 times each night. And even if we're only in there for a couple min each time, it is taking its toll on our own sleep!

DH and I sleep in separate rooms so at least one of us can get a good night's sleep, which is ridiculous. Ferber does suggest putting twins in separate bedrooms to fix problems, but that's not practical for us - the only other bedroom is right next door where screams would wake up the other twin anyway. So, we will have to deal with this as they share a room.

I am going to re-Ferberize tonight - when one cries I'll go in and offer water/blanket if asked but then I will simply say go back to sleep, see you in the morning, and leave - and if she scream I'll check in at intervals.

I'm also considering a sticker chart because (like anyone) I would love to solve this without excessive crying. How well do you think this would work for 2yos? A nice pretty sticker for every quiet night? At this point we don't WANT to try less than 11.5 hours of sleep - it's too hard for us - we have no time to ourselves! - and if they truly need less sleep (which would be SO unfair!), they will have to learn to lie quietly at night when they wake. But I don't want to try a sticker chart if it's only going to add to their frustration. FWIW, our girls are quite verbal and seem to really understand a LOT. DD2 (the worse sleeper) even uses words like "either" and "instead", "me" and "myself" correctly.

They are 27 months, so not really old enough to drop the nap. And like I said, I will ask the daycare to further limit their naps, but I'd really hate to have to do that. Daycare says they always fall asleep easily for their naps.

And on a side note - what do others' DCPs do when children get to the age where they drop a nap, so that some kids in the class need naps while others don't?

Any suggestions welcome!!