Moving from cots to beds

[SweetieTime]

We moved DTs from cots to beds back in October and since then bedtime has been very difficult.
They have just turned 3 so done well keeping them in cots this long. They share a room which is the problem as they keep each other up, wake each other up, encourage each other to be misbehaving. They are potty trained but they wear nappies at night. But they often go soon after going to bed, despite me sitting them on potty/loo, then 'clean' each other up usually ending up with more mess on the carpet than cleaned.
I have tried leaving them, staying with them, patting them. Nothing seems to work. We still put them to bed at 7 but it can be 9 before they are asleep. Then they are waking each other up before 6 when before they were often still asleep at 7am. They are so tired during the day they are over emotional, whingy. They don't nap anymore since going into beds either unless driven around.
Surely other parents have children sharing a room. How do you do it?

I've got no experience of twins or room sharing, sorry, but I didn't want to read and run. I

was wondering whether starting the bedtime routine a bit earlier might help, so that they eventually fall asleep at an earlier time?

Also, maybe a reward chart for staying in their beds? They're old enough to get the point of a reward chart so it could be helpful. Some children also respond to a gro-clock, so they know if they wake early its not time for getting up yet.

I'd also take them for a wee before bed, if you don't already, and perhaps limit drinks after a certain point in the bedtime routine too.