I agree a lot with what 5 monkey's said. I let them cry it out. I go back in after about 20-30 minutes and lay the child back down, say goodnight in my happy voice and leave again.

I also started with everyone in the same room. That didn't go over well. I now put the more difficult napper(s) in a separate room.

I am firm with the children. There is no playing allowed, they must be quiet while going to sleep or if they wake early and they must remain in their bed. If the little ones start to cry within the last half hour I will go take them out of the room and put them on the couch with some books. I certainly don't want them waking the whole room! They also learn quickly that they must stay put and be quiet.